All the alternatives I can think of are extremely time-intensive - you'd have to go back to everyone who already scanned in and check their id against their boarding pass. That would add significant delays in taking off, which could cost the airline a lot of money in ripple effects throughout the day and will certainly cost the gate agents a lot of hassle and ill-will from customers.
It's a good question as to whether they have a protocol for this; if the scanner is prone to making mistakes even 1 in a 1000 times, that's every few flights, several times a day. It wouldn't be worth it to the airline to have a time-intensive protocol to check.
I think surfacing additional information would help increase confidence in the system when it raises a problem.
For example, keep a running passengerCount (or rather display it since it must(?) exist).
If someone has a copied pass, their screen can show:
Current Passenger Count 10
This Pass Last Scanned at 5
If the fraudster & legitimate passenger are back-to-back, that might add some confusion for the agent so they'd need a good way to display this. They can call out to the last person to come back to clear up confusion.
If the fraudster was much earlier, they'd have to go find them. Maybe take a picture of each passenger during pass-scan.
Or simpler: this would be simplified by using Steffen Method boarding [1]: you should know exactly which seat matches a given passenger count number.
> All the alternatives I can think of are extremely time-intensive - you'd have to go back to everyone who already scanned in and check their id against their boarding pass. That would add significant delays in taking off, which could cost the airline a lot of money in ripple effects throughout the day and will certainly cost the gate agents a lot of hassle and ill-will from customers.
I've had to do exactly that before. Whole plane: deplane, re-scan boarding passes, re-board.
Somehow we had one too many people on the plane on a full flight, exactly like this scenario. Of course it was the one guy that was making so much noise about "who gonna get in trouble" and "this [is] like a reality show."
It's a good question as to whether they have a protocol for this; if the scanner is prone to making mistakes even 1 in a 1000 times, that's every few flights, several times a day. It wouldn't be worth it to the airline to have a time-intensive protocol to check.