I am so sick of people trying to tell me that since the F-15 and 16's O2 system works the Raptors should be easy to design.
The F-22 operates in a different envelope which creates many more engineering challenges and physiological problems than that of the F-16 and F-15. Sadly, even a USAF cadet did not understand this (he flies AT-6 Texan IIs)....but I guess that is why he is not in engineering