I'm remembering the ISBN switch, which I thought would throw off some older systems—and it probably did, but it took so long to happen that the transition ended up being pretty smooth. The key element was that for a solid ten years or so, every book had both an old-style and a new-style ISBN (and possibly some still do).
I'm hoping that behind the scenes they really are looking at a better plan than just "work around it", but the workaround can buy them time; and if their operations plan is strong, they'll be able to roll it out very slowly in parallel while all their back-end stuff gets upgraded. (This would require some aspect of the new system to make it immediately distinguishable from the old one, e.g. three-letter airlines or whatever, but that's a minor detail compared to all the other stuff they'd have to work out.) Bonus points if knowing the "old" number lets you algorithmically derive the new one somehow, and vice versa, to make the transition period easier. :)
I still love the bit of book trivia that since 13 digit EAN's start with a country code, you can convert an ISBN-10 into an ISBN-13 by prepending it with the code for "book land" - 978.
(I worked on Library Management Software for 6 years).
I also used to know what most of the MARC 21 (library interchange format) codes stood for ... but that has now been purged from the memory banks ... except 245 $c - statement of responsibility https://www.loc.gov/marc/bibliographic/bd245.html
> I'm hoping that behind the scenes they really are looking at a better plan than just "work around it",
Airline-IT is mostly just a big pile of workarounds to cope with limitations from 40+ year old systems. I've worked with reservation systems and seen their modernizations through the years. Modern xml-formats shoving megabytes of data for every reservation. They are very wasteful, generously designed with redundant fields, long feature-lists and all kind of annoying shit. But at the end, your whole booking can still drip on the passenger's name being one character too long. Even after decades and multiple iterations of interfaces, at the core the systems today still depend on whatever someone in the 1960s considered as good enough for the US-market.
I'm hoping that behind the scenes they really are looking at a better plan than just "work around it", but the workaround can buy them time; and if their operations plan is strong, they'll be able to roll it out very slowly in parallel while all their back-end stuff gets upgraded. (This would require some aspect of the new system to make it immediately distinguishable from the old one, e.g. three-letter airlines or whatever, but that's a minor detail compared to all the other stuff they'd have to work out.) Bonus points if knowing the "old" number lets you algorithmically derive the new one somehow, and vice versa, to make the transition period easier. :)