Economically, older cargo types can make a lot more sense than a new plane. With the 744 no longer in production, a used model with another 15 years of use at $50mn is a better investment than a new 748 at its $400mn list price. Well-capitalized wet lessors like Atlas can afford to invest in new frames, but if you're a startup or a primarily passenger airline looking to branch out into a few cargo routes, you can't necessarily afford to buy new.
A similar trend occurred with the MD-11. Only a hundred or so frames exist, the last one built in 2000. As a passenger airplane, it was not great: high deck angle in cruise, noise, and of course poor fuel burn compared to projections. But for freight, its nearest competitor is the 77F. A few years ago when I was looking into this, a used MD11 frame would go for around $3mn. With a D-check you could have it flying again for an all-in cost of maybe $10-$15mn and it would last another 10 years. The 77F lists for around $200mn. Thus, even though the M11F is far less efficient than the 77F, it would be 10 or more years before the fuel costs would make up the difference in initial outlay. This is why the MD-11s are still flying.
Passengers prefer new planes, but cargo doesn't complain!
Overnight cargo carriers like FedEx additionally have economics that make this worthwhile. Those planes might typically make only two flights in a day, one to a hub in the evening and one from the hub in the morning.
The efficiency of modern planes is only worth the price if you fly them constantly.
Likewise, this is why there are still freight companies flying (older) aircraft with a three-man crew, including a flight engineer (or four with a loadmaster). Yes, you have to pay an extra crew member… but the initial outlay can be much lower.
My father in law just switched to the triple 7 after a few decades on the MD-11 out of Anchorage. He loved the plane but even with the top spot on seniority the routes kept getting reduced making the 777 more desirable. He often commented that ATC always did a poor job of accounting for their higher approach speed when placing them into the lineup, as they about every other plane out there can fly much slower.
It's interesting - in the current low rates environment, I'd have thought that the initial outlay is much less relevant. On the other hand, even a paltry 2% are $4m a year on a $200m 77F.
Turning this around, though, we should see even more older planes being kept around once rates rise significantly.
Suitability for conversion to freighter service was actually one of the original design goals for the 747! But back then, the assumption was that passenger airlines would be transitioning not to twinjets but to supersonic planes.
Also airlines are moving from the hub and spoke model to the point to point model. So the need for 747's and especially A380's for passenger service has gone way down. Plus both those planes just aren't as efficient as twinjets. In fact, it was partly the high fuel consumption of the early 747's that eventually led to Pan-Am's bankruptcy.
If I read it correctly, the original design was for an AF cargo plane, actually. As the AF dropped the Boeing proposal, airlines asked for a larger plane, and Boeing converted the freight design into a passenger plane. So no wonder, you could so easily convert it into a cargo plane.
AFAIK, relatively little was shared between the proposed Boeing transport and the 747. Certainly there are influences: the cockpit and the nose door are the biggest ones. I think little else was carried over, given very different mission profiles.
(The winner of that competition was the C-5 Galaxy.)
When Boeing stretched the upper deck for the -300 and subsequent passenger models there was resistance from the freight operators because the floor beams intruded into the main-deck volume. Not so much as to affect passengers but enough to restrict positioning of cargo.
So all built-as-freighter models retain the short-deck with short hump, right up until the latest 747-8F being built today. Even though, counter intuitively, the long hump has less drag.
That's also why retired long-hump passenger versions are less valued for conversion to freighters. There is no approved type mod to hack off the long hump and its structure.
> Even though, counter intuitively, the long hump has less drag.
Not directly related but readers may be interested in the Area Rule. This is more aimed at trans and super sonic flight so I don't think that applicable to the 747. Basically the whole area cross sections down the length of the plane needs to be smooth so when it's punching a hole in the air the compression ( volume displacement ) around it is even and this reduces drag. The generally do this by narrowing the fuselage at the places the wings and external engines are.
No, planes are not designed with a significant amount of lift from their bodies (excepting lifting-body aircraft like the B2). The primary goal for the body design is to reduce drag, and let the wings produce the lift.
Wendover Productions did a great video YouTube on overnight shipping that goes into the use of old planes for shipping cargo. [1] . The short version is that cargo planes spend most of their time sitting around, usually much less time than an equivalently sized passenger plane.
Although due to its size, 747F are usually used at a higher percentage of the time. The large freighters (7437, 777) are mostly used between hubs and for long-distance routes. That's why having fuel efficient planes (e.g. 747-8) makes sense.
What Wendover describes are cargo planes serving hubs, those often only fly 1-2 returns a day, so having a very cheap plane with higher consumption is worth it (e.g. A300).
Also four engines are a must if you operate long haul from hot and high airports like Mexico, Bogota or Quito. Due to engine failure performance requirements a twin engine needs to cut back almost half the traffic load(cargo and passangers) to be able to take off within the tables.
Once they have to retire 747 and A340 airlines din't really know what to do in those airports. New hot and high versions of the twin engines are being studied, but they have failed to meet the expectations previously.
The airlines now ferry around extra fuel from airport to airport as well. Some logistics smarty-pants figured out the airlines can save money this way. (Basically doing arbitrage with regional differences in fuel costs.)
Is there an attachment point on the other side as well? Being super-cynical, I can't help but wonder if these attachment points were also added just in case existing fleets of 747s were pressed into service as long range bombers...
I was once in the back of a 747, on the left side, when I noticed that the inboard flap section was jiggling about, even though it was retracted. I tried to remember if that was normal, and was about to get up and look at the other side, when the captain announced that any turbulence we might notice was on account of the extra engine under the wing, being ferried as a replacement for a failed one.
A question, for anyone who knows about these things: when an engine is being ferried like this, are the fan and compressors locked in place, or allowed to spin in the airflow? I would have thought that locking them would impose unnecessary loads on those parts and create extra drag and turbulence, while allowing them to rotate would require lubrication?
I'm no expert but based on these photos [1] it looks like they're only transporting the engine core. What we normally call an "engine" on an airliner is really a relatively small engine core with a huge fan on the front. The white donut-like object is probably blocking airflow through the core to minimize drag.
There are many military versions of the 747. Check out the wiki page.
> 747 CMCA – This "Cruise Missile Carrier Aircraft" variant was considered by the U.S. Air Force during the development of the B-1 Lancer strategic bomber. It would have been equipped with 50 to 100 AGM-86 ALCM cruise missiles on rotary launchers. This plan was abandoned in favor of more conventional strategic bombers.
Huh, well I guess that answers my question. I can't see anything about this being used as a mounting point for heavy bombs (which is where I was going with that) but I guess you can't build a large flying platform without at least considering how to strap weapons to it.
No, there is one mount just on one side and the engine also has to be prepared for ferrying. There are quite a few planes which can do this, sometimes the engines have a pod put around them, in this case I think the fans are removed to reduce drag.
In all cases, the engine isn't working. Think of it more like putting an engine on your car roof rack.
Ah, OK. I read it as upgrading it to a six engine bomber and carrying the load internally - that would require significant airframe modifications though so probably a silly idea.
Given the rest of the Air Force fleet I can't see that a 747 with one bomb would the that useful, but it's one more airframe I suppose. It would also need to be fitted with the arming and release mechanisms so quite a lot of additional work involved there too.
Yeah, that was my thought. I bet you could fit an awfully big bomb under there... or a long range tank with enough fuel in it to keep you in the air for a day or more.
747 was developed in the 60s when it was clear that ICBMs were the future of long-range bombing. I doubt they were thinking of military applications with this. The only long-range bomber missions envisioned by that time were super-sonic deep penetration designs (e.g., see XB-70 bomber), and even those were abandoned in the face of improving anti-aircraft missile tech (see: when the Soviet Union shot down a U-2).
I dunno, something the size of a 747 is probably already flirting with the limits of diminishing returns. It's not unlike the rocket equation. Fuel is very heavy, so adding more fuel means you burn more fuel, meaning you need to carry more fuel...
The first 747 is at the Museum of Flight in Seattle and it is actually set up for inflight refueling. Quite the versatile platform! You can see this at the very back in the 3d tour (or in person, it's a great place):
I bet there is an attachment point and another engine on there to balance things out.
I would be surprised if Boeing considered or purposely designed in some long range bomber capabilities into the 747. Maybe though as part of the sales pitch to countries that would like to add military capability in a low key sort of way...
Don't forget the MD11, also a favourite of the cargo operators due to having plenty of spare thrust for hot and high ops. Although it's also a truism that high altitude locations don't generally have a lot of heavy things to export. AFAIK Quito's main outgoing cargo is cut flowers...
Mexico main cargo are avocados for Europe, Bogota fruis and flowers too. There isn't enough cargo offer for the demand that exists now a days. We are leaving cargo behind every single flight between these airports and Madrid.
Fun fact: The loadmaster and maintenance workers on Flexport's 747 freighter fly back and forth on the plane 20 days per year, sleeping in the old first class seats in the upper deck. That is real skin in the game.
The plane began service as a passenger plane for Japan Air in the 90s. I better its safer than most modern planes with those guys living up there taking care of her.
Cargo planes are generally less safe than passenger planes, this is due to factors like the pilots (less money for cargo pilots) and the hardware they're flying (older disused passenger planes being flown cargo).
Fun fact: NCR flight 102 had the loadmaster on board, but is probably one of the most spectacular caught on camera crashes of a 747. (It's the one where it looks like it falls out of the sky on take-off) It was also most likely the loadmasters fault.
https://en.wikipedia.org/wiki/National_Airlines_Flight_102
Re: cargo pilots earning less, is that true? I’m in Memphis, and all the Fedex pilots I know make a ton of money. Most are ex-military. Most of the planes are definitely older (DC-10/MD-11s trijets!) but they are being aggressively phased out for new 777s to save on fuel.
My understanding based on what I hear from friends in the industry is that this is definitely not true, especially earlier on in a pilot's career. If one plays their cards right, you can make a good deal more as a 'cargo dog' pilot when you're young, compared to working for a regional or non-major airline, which is where most younger passenger pilots begin their careers. However, the disparity in pay can be more pronounced later on, as senior pilots at the major airlines can in many cases make much more income, or have a much better work-life balance.
Did a little googling as I was curious, and sure enough, wow Fedex pilots are well paid. Also, I know that while Fedex pilots typically fly overnight, its only a few times a week and they have the ability to be around for daytime events. One of my lacrosse coaches in high school was a Fedex pilot, and he seems to do quite well while being available to arrange his schedule. All-caps emphasis mine below, Fedex is dramatically higher.
"According to Memphis newspaper The Commercial Appeal, pilots flying for FedEx earn closer to $234,000 a year ON AVERAGE -- 90% more, to carry boxes from Point A to Point B, than the folks flying actual human passengers make.
https://www.fool.com/investing/general/2015/09/05/pilots-are...
"Salaries at Delta Air Lines Inc range from an average of $42,495 to $144,385 a year. Delta Air Lines Inc employees with the job title Airline Captain make the most with an average annual salary of $188,104
>I better its safer than most modern planes with those guys living up there taking care of her.
Not likely. Planes don't usually crash from maintenance neglect. We are at a point where it's multiple simultaneous failures caused by something unforseen, not lazy maintenance.
We use this model in the manufacturing plant I work in.
You can cut a small corner every single day and it probably won't matter, until that one time when some other upset condition occurs and suddenly you're seriously injured. An implementation of this has made a huge difference in the overall safety record.
There's an excellent book, The Checklist Manifesto by Atul Gawande, that explains several transfers from aviation best practices to hospital best practices (primarily checklists and CRM, crew resource management). Captivating read if you're interested in aviation and not dying needlessly in hospital.
Possibly from the same source but one useful thing I learned was to do with check lists. Rather than ticking a box to say how many scalpels you used, is the tyre pressure OK etc etc you write down the number. The persons doesn't just say yes OK, they write down the pressure. That [generally] ensures they have actually measured it and got a real value.
Was listening to Bloomberg Radio this morning and Tom Keene brought this up randomly...I was surprised to hear only ~1500 were ever built; seems like a low number for a plane that's been around since the 1970s. One thing I have always wondered about tho is, where are the relatively short domestic route (2-3 hours) where a 500+ person 747 would make sense? It's almost like airlines need the inverse for which this plane was made. Same goes for the A380.
On a related tangent, there was a general expectation that the A380 superjumbo would find a lot of customers on core domestic routes between Chinese and Indian megacities like Beijing-Shanghai, Mumbai-Delhi, etc. Aside from the odd filler hop between long-haul flights, this has entirely failed to materialize: there's tons of traffic between these cities but the vast majority is single-aisle 737/A320.
It's similar to NYC-LAX or NYC-SFO. Airlines realised that passengers prefer 10 flights a day with a small plane rather than 4 a day with a large plane. Boarding/deboarding is faster on single-aisle planes and it gives more flexibility on travel times. Operating costs for large planes are also not lower, as long as you can get landing rights. So apart from a few overcongested airports (e.g. London Heathrow), there's really no reason to use a large plane if you can use a small one instead.
> Airlines realised that passengers prefer 10 flights a day with a small plane rather than 4 a day with a large plane.
That isn't relevant or news regarding the A380. The A380 was designed to connect hubs in a hub and spoke model. Thus they were designed expecting to operate under the 10 flights a day scenario. Yet, if airlines bet on point-to-point services that have a limited demand then there goes the demand for higher-capacity planes.
Even with hub and spoke, more flights are better. If you have enough runways/gate capacity, you can increase frequency and keep connection times lower than with few A380 connections. The A380 was a bet on missing capacity but so far, only DXB and LHR really have this problem.
> Boarding/deboarding is faster on single-aisle planes
No, the complete opposite is true. Boarding and deplaning are far more efficient with twin aisles. The other features you mention are correct, however. Lower operating expense, more flexibility of routes, are why smaller twins are more successful while the VLA are being relegated to the cargo market.
Theoretically it should be faster on twin-aisle. However, you tend to get more passengers/door on twin-aisle planes. A A320 with max 180 passengers is boarded through 1-2 doors, a A380 with up to 600 passengers through 2-3 doors. They could use 7 doors for the A380 but no-one is doing that (refuelling and cargo unloading also takes longer). Other long-haul planes are often boarded through only one door (or the second one for <20 premium passengers). That can lead to boarding times of 30 minutes for a long-haul plane, compared to ~10 minutes for A320/B738 through one door (values from experience).
Look at Sydney <> Melbourne. One of the busiest routes in the world (second by number of flights) - Qantas itself operates 60 flights a day between the two - flown almost exclusively on B373s and A320s.
But the amount of gates is pretty much fixed. As Asia becomes richer you can see large populations now demanding seats. Perhaps the A380 was built a few decades too soon...
Maybe in a lot of US/European airports that originally date from the first half of the 1900s, they're too close to the city center and don't have enough land to expand. Even then, they seem to be regularly able to find ways to get more gates in renovations (ex: Newark/EWR's Terminal A replacement is going to have the ability to be expanded for 12 more gates). I'm sure there's an upper limit, but plenty of those older airports can find space for more gates in modern redesigns.
Most of the big modern airports were built with massive expansion in mind. Well outside the city centers and with large land areas that they already own (and so won't be developed).
You can turn-around a A320/B738 in ~20 minutes (low cost carriers do that frequently), a A380 is really challenging to turn around in less than 1 hour. Furthermore, the A380 will need space of ~2 A320/B738. So per given space and time during peak hours, small planes can actually get you more capacity than large planes. You could change that (boarding A380 through 7 doors, probably faster refuelling) but planes like the A380/B747/B777 were never designed for quick turnarounds.
Boarding/deboarding is such a frustrating experience in planes: people are just too damn slow. Many people are fine: they can stand up, grab their bag out of the bin, and start walking within 2 seconds, but other people are just ridiculous.
There should be a test and certification for plane passengers, where people who can demonstrate proficiency in boarding/deboarding are given priority over everyone else, so they don't have to wait for the slow people.
> There should be a test and certification for plane passengers,
This already exists, it's called ability to pay for business/first class. Increasingly, at least in America, seats near the front are getting more expensive too.
People in first class are generally rich, which means they're likely to be older, which means they're probably going to be slow too. The main advantage is that there's fewer of them since the first class section has far fewer seats than coach.
I'm thinking of a system where people who have demonstrated an ability to very quickly stow a suitcase in the overhead compartment and get in their seat and out of the aisle, and then stand up, grab their suitcase, and start walking down the aisle, and do this in formation, are given special status and put in a special part of the plane as a reward for their efficiency. This would probably improve the process overall, as well as encourage people to stop screwing around so times improve overall. Maybe they should even have training classes for this.
This reminds me of the difference between car drivers: some of them can jump in the driver's seat and pull out in a few seconds, and others take 5 minutes doing--I have no clue what--before they can start driving (and I don't mean people plotting directions with GPS either, I saw plenty of this behavior long before people had smartphones or GPS). That latter group is probably the same group of people who make airplane boarding/deboarding so agonizingly slow.
I'm not convinced there's anyone within the aviation industry that doesn't respect the 737. (Which was of course designed for a much more common use case anyway)
Sydney to Auckland Qantas flights used to be on the 747 (3 hour flight time). It was always quite weird to get on such a massive plane and not feel like the plane had really gotten up to altitude before it was already preparing to land.
My first ever experience with business class was when I booked a Melbourne to Sydney flight and it happened to be on a plane that was doing Mel-Syd-LA in a 747. We were one of the few passengers doing just the Mel-Syd leg so we all got bumped up to business class for the 90 minute flight.
Not an aeronautics expert, but my understanding is that the 747 design sits on a local maximum, with regards to figures like wing loading. The A380 deliberately gets bigger by aiming for a less ideal design. Its wing loading is a bit high. I suspect that this tends to make it less suitable for cargo than the 747.
Wing loading is a complicated thing... higher wing loading will increase takeoff and landing speeds a little bit, but it also generally makes for a smoother ride in flight.
Interestingly enough, per-passenger the CO2 emissions are almost certainly better for the ship, but sulfur, particulate, and other emissions may be much worse.
The title is a bit clickbait-y: passenger 747s were retired by the US airlines last year, and are not coming back. Passenger to freighter conversions (the BCF, Boeing Converted Freighter) are also not restarting. And, it’s highly unlikely there will be any new passenger 747s manufactured.
The headline isn't really wrong. According to the article, they're not being retired at the rate which seemed likely--because of freighter demand (at least so long as fuel prices stay relatively low). But, for someone no familiar with 747s, the headline does seem to imply that this unexpected use was discovered for them--which, of course, isn't the case.
Planes are an easy target because they're so big, but the industry as a whole is hyper-focussed on efficiency. If you want to rail against emissions, don't look at the plane, look at the endless procession of single-occupancy 2 ton cars the plane is flying over.
And you can get a lot of parcels on a plane like the 747F. Amortised by unit the emission numbers are in fact very good. It's almost certain that your last fast food run or uber trip used much more gasoline than it took to get your last parcel all the way from China.
But why let the facts get in the way of some good old righteous outrage!
How bad it is depends on what you're comparing it with. The shipping industry might have relatively retrograde attitudes towards pollution, but air freight still uses something in the order of 100x more carbon per tonne km than sea freight which is often a close substitute. 1990s 747-400s brought back into service aren't exactly the most energy efficient aircraft either. On the other hand, you could still fly a tonne of stuff for a few hundred miles for the estimated carbon cost of a single Bitcoin transaction...
A fast food run (on the ground local transport) can become electrified and run on renewables. Flight transported goods is much harder to make run on renewables. Even if a flight runs on 100% biofuels, the high altitude climate forcing effects of the emissions seems to be unavoidable and are as big as the CO2 emission itself.
To avoid going over the average 2C temperature rise we are going to need to cut all these emissions. Air transport emissions will become a hard nutt to crack.
One could make just as vaild of an argument for the other way around.
Telling people to "just don't click the 1-day shipping option" is like saying "just ride the bus" it's not that simple and while it's not straight up tone deaf it's a far cry from perfect pitch.
* get a smaller car, one that uses less gas and pollutes less
* share a ride
* ride the bus, take a train/tram/trolley/ferry/etc.
* ride a bike, e-bike, scooter, motorcycle
* and another million improvements or alternatives
Meanwhile, if I'm Romania and I want to order something from Japan, as an individual or company, I either order by plane, in which case it probably arrives in a few days, or I wait a few months.
If I want to fly over there, my only realistic option is flying...
The gap between "must have" and "nice to have" is much, much higher between land transport and air transport.
You're comparing things that aren't comparable. Of course single occupancy cars are inefficient, but that shouldn't obscure the fact that long distance transportation is a major source of emissions that should be severely limited. The fact that the industry is efficiency focused is also irrelevant at best, because they are high emitters in spite of it.
Airplanes account for 5% of global emissions. Ground transport, 40%. Presently, the low hanging fruit is ground not only because of its much larger share of emissions, but also because transitioning to renewables is easier (at least today) for road than air vehicles.
Noone is going to "severely limit" air transport due to its emissions. Doubling the cost of oil, maybe, but not emissions.
Ironically a heavy push to electrified cars would reduce demand for gasoline, potentially dropping the price of oil and saving money for airlines and reducing ticket prices. The final result would be increased air travel and CO2 emissions from air travel.
Overall still a win for the environment, but not as much of one as people would want.
> Noone is going to "severely limit" air transport due to its emissions
If no one does it (and many other radical changes), we will have 4+°C warming and a major global catastrophe. I'm not optimistic, but that's what should be done.
it seems like people in countries like mine (rich, western) find it very easy to blame the supply side of the equation rather than the demand side of the equation -- e.g. companies are to blame for wrecking the environment because they ship stuff in planes to save money / save time. but the general public are also to blame as the source of demand.
what might make a huge positive difference for the environment would be rolling out policies to help reduce population growth (or the absolute population count) of people such as myself with relatively affluent polluting lifestyles, but we might have to wait until there is mass suffering right here right now due to environment reasons across many countries with political power before there is substantial change.
>>...the general public are also to blame as the source of demand.
Yes, but companies have absolute control over what mode of transport is used to do shipping, not consumers. Demand is good for the economy, so you do not want to quash it. You DO want companies to satisfy demand responsibly.
In the maritime trade industry, we can absolutely fuel global shipping 100% on GHG emission-free renewables using H2 fuel cells. The tide is starting to turn, albeit a little too slow for my taste. Granted, the challenge is exponentially harder for extreme high power density kWh consumers like aircraft. Ships are very high kWh consumers, but don't have the power density of aircraft, so much lower density/higher weight fuels and engines can be employed that makes the problem significantly easier to solve.
...Also, Thanos, please count me among one of your childless population growth inhibitors. I don't dissagree with you there.
Carrying large tanks of compressed hydrogen on merchant ships isn't safe or practical. Sustainable carbon-neutral liquid bio-fuels are a more likely long term solution. Those can be used with minimal changes to our existing transportation systems once the production cost comes down.
H2 fuel is absolutely practical and we're integrating it into designs as we speak. However, we are using Cryogenic Liquid H2 (conforming to IMO IGC(1)) which msy be stored at atmospheric pressure, not compressed gas, although additional regulations for shipboard H2 storage are emerging as the popularity grows(2). It's not dissimilar from carrying LNG.
Biofuels still release GHG's (2), not just carbon), and it's arguable how much is recovered. The Nitrogen released still contribute to acid rain. Why go through this messy hassle and guessing game when we already have a perfectly environmentally clean cycle of breaking down H20 into H and O2 via renewables, then recombining the H with free O2 in fuel cells to produce e- and exhaust only water?
Breaking down water into hydrogen and then processing it through a fuel cell is very energy inefficient. Unless we have some breakthrough efficiency improvements, hydrogen fuel will probably never be economically viable on a large scale.
I hear this argument all the time, and asside from being unfounded, it makes absolutely no sense. Even in it's infancy, H2 cost is just a little higher than gasoline at the pump (1).
From someone who works in the sector on a daily basis, H2 production from offshore wind powered electrolosis is (and will continue to be) growing to meet increasing demand.
The energy to perform electrolosys comes from renewables like wind and solar, the efficiency of which (primarilly concerning the fully burdoned CAPEX/OPEX of renewable power plant to shipboard fuel cost - i.e. tnhe "cost at the pump") is certainly competitive with diesel fuel prices when you factor in efficiency gains of fuel cells over diesel engines over the full range of power loading. Not too mention the indirect envoronmental gains cost avoidance engine integrators realize by not having to buy additional pollution abatement systems (e.g. EGRs, Scrubbers, SCRs, etc).
We have to be careful with massive new demand for biofuels. Even small changes to e.g. ethanol policy have caused food shortages (well, higher commodity food prices, but at some level these are equivalent) in the past.
i agree. it is likely this change to use air freight instead of some plausible alternative form of freight is more profitable and more polluting, so i agree it is likely a change in the wrong direction.
i suspect air freight has a relatively minor impact compared to other sources of emissions. e.g. for energy estimates (not emission estimates), the without hot air book estimates that passenger plane flights burn far more energy per capita per year than the energy used to transport "stuff": https://www.withouthotair.com/c18/page_103.shtml
it'd be helpful if there was a global (or pseudo-global) tax on carbon so that climate impact could be priced in and could have greater influence in commercial / economic / government decisions, but alas.
A similar trend occurred with the MD-11. Only a hundred or so frames exist, the last one built in 2000. As a passenger airplane, it was not great: high deck angle in cruise, noise, and of course poor fuel burn compared to projections. But for freight, its nearest competitor is the 77F. A few years ago when I was looking into this, a used MD11 frame would go for around $3mn. With a D-check you could have it flying again for an all-in cost of maybe $10-$15mn and it would last another 10 years. The 77F lists for around $200mn. Thus, even though the M11F is far less efficient than the 77F, it would be 10 or more years before the fuel costs would make up the difference in initial outlay. This is why the MD-11s are still flying.
Passengers prefer new planes, but cargo doesn't complain!