Have you been involved with the engineering of aircraft control systems, or are you just speculating?
The attrition rate is terrible and its impossible to keep people who have knowledge of the program on board.
I would guess that 30-50% of our team are inexperienced java software engineers with less then 5 years of working experience. Around 100 people work on our project but there are probably 3-5 people who still have a clear picture of how everything is working / supposed to work.