The Air Force is allowing  F-35A Lighting II aircraft at Luke Air Force Base, Ariz., to fly again, without fully determining the specific root cause of the problem that led to their grounding 11 days earlier. According to Air Force Times, the aircraft’s pilots reported five incidents of oxygen deprivation during flights that took place between May 2 and June 8. While the Air Force and Lockheed Martin, the plane’s manufacturer, could not pinpoint what led to the oxygen deprivation, they implemented a protocol aimed at addressing maintenance and aircrew flight equipment procedures. Pilots were instructed to:

•      Avoid altitudes in which the incidents occurred;
•      Alter ground procedures to mitigate risks to pilots;
•      Include better communications between pilots and medical communities, as they relate to the oxygen-deprivation incidents;
•      Increase the levels of backup oxygen systems on each flight;
•      Give pilots the choice to wear sensors, which would be used to collect relevant data.