No.4 HAMILTON PLACE
National Aerospace Library 
The USAF has confirmed that a handful of Lockheed Martin F-22 pilots have refused to fly the jet, after the mysterious flaw causing hypoxia-like effects appears still unresolved.
The Raptors were grounded in 2011 for nearly five months after a fatal crash implicated a lack of oxygen in the accident. However since the F-22s returned to flight in September, the USAF has since experienced non-fatal 11 incidents, with the cause still unknown.
