This means that it has long term support for the life of the airframe which for passenger airliners can easily by 50+ years (see https://en.wikipedia.org/wiki/Boeing_737 which is still flying after 50 years).
Companies like that often just buy up a stock of the hardware they need and stuff it in a warehouse, at least when it's in danger of being discontinued. They don't need to maintain the source code at all. They just need to be able to keep installing the binary.
https://twitter.com/copiousfreetime/status/67583454330408140...
This means that it has long term support for the life of the airframe which for passenger airliners can easily by 50+ years (see https://en.wikipedia.org/wiki/Boeing_737 which is still flying after 50 years).