Air Force leaders provided an update on the Air Force Scientific Advisory Board study into the F-22 Raptor life support systems. From April 2008 until May 2011, the Air Force experienced 14 physiological incidents with the fleet of F-22s, noticed a pattern of unexplained hypoxia-like physiological incidents. The USAF have taken precautionary measures such as installing activated-charcoal filters, oxygen sensors, and having pilots wear a pulse-oximeter. But despite the «mitigation efforts,» there continues to be incidents recorded every month.

 
More information:
**  USAF vows to discover root cause of Raptor’s maladies
       Flight Global / Dave Majumdar / 29-03-2012
** AF Scientific Board Says F-22 Pilot Safety a Priority
      Mitch Gettle / Military.com News / 02-04-2012