Planes have just as much spaghetti code as anything else, the only difference is that it's extremely well tested (functionally) and verified spaghetti code.
Planes have just as much spaghetti code as anything else, the only difference is that it's extremely well tested (functionally) and verified spaghetti code.
It's not hard to imagine there would be even more than in less verified fields, since if you try to clean it up you need to verify it again too.
From talking to someone in the industry TDD seems to be a popular methodology.