"We continue to implement improvements to the aircraft's life support systems and are carefully collecting and analyzing operational, maintenance and physiological data for all Raptor flights," said Maj. Chad Steffey, an Air Force spokesman.
Read more here: http://www.adn.com/2011/12/21/2227997/fatal-problems-plague-f-22-americas.html#storylink=cpy
lets hope that a functioning life support system is considered a "improvement" :(