After an 11-day pause, the 56th Fighter Wing on Wednesday will resume local F-35A Lightning II flight operations, officials said Monday evening.

All F-35A flight operations at Luke Air Force Base in Arizona were canceled June 9 after five incidents in which pilots experienced symptoms similar to hypoxia, or oxygen deprivation.

Flight operations will resume Wednesday, although no specific root cause for the physiological events was identified during recent visits from experts and engineers from the Joint Program Office, Lockheed Martin, the Air Force Research Laboratory and other organizations, said Maj. Rebecca Heyse, a spokeswoman for Luke Air Force Base, in a statement. 

Lt. Gen. Bunch on why the US needed to showcase the F-35 in Paris

The flight of the F-35 was a little uncertain for a period of time prior to the Paris Air Show, but it came and enthralled. And that sends an important message to the international community, said Lt. Gen. Arnold Bunch, the military deputy of the Office of the Assistant Secretary of the Air Force for Acquisition.

"However, specific concerns were eliminated as possible causes, including maintenance and aircrew flight equipment procedures," Heyse said.

The decision to resume flight operations at Luke Air Force Base comes as the Air Force showcases the F-35 at the Paris Air Show.

When flight operations resume Wednesday, five criteria will temporarily be applied as technical and human performance data is gathered, Heyse said.

They are:

  • Avoid the altitudes in which all five physiological events occurred.
  • Modify ground procedures to mitigate physiological risks to pilots.
  • Expand physiological training to increase understanding between pilot and medical communities.
  • Increase minimum levels for backup oxygen systems for each flight.
  • Offer pilots the option of wearing sensors during flight to collect airborne human performance data.

"Our active duty, reserve and international team has worked tirelessly to better understand the physiological events," said Brig. Gen. Brook Leonard, the 56th Fighter Wing commander, in a statement. "This is a complex challenge that necessitates multidimensional solutions across a series of steps to get back to a full operating capability. We are confident that this initial step with the criteria our team developed will allow us to return to flying F-35s safely and to continue building the future of airpower."