After taking off to the skies following their grounding due to hypoxia issues, the US Air Force F-35 pilots at Luke AFB are once again facing similar problems. Since Luke F-35s resumed flying, pilots there have reported five physiological episodes (PEs) with pilots reporting tingling fingers and other symptoms that indicate hypoxia. 

The commander of the 56th Operations Group and an F-35 pilot Col. Ben Bishop told Aviation Week in an interview dated 23 October that the symptoms were milder than in the initial five events, and in each instance the pilots were able to safely recover the aircraft. 

The rate of PEs in the F-35A is significantly higher than in the other F-35 variants. Overall from 2006-2017, the Joint Program Office recorded 29 PEs across all variants of the F-35: 20 in the F-35A; four in the USMC F-35B; and five in the US Navy F-35C.

As the symptoms may be indicating some other physiological states than hypoxia, such as hypercapnia (high levels of carbon dioxide in the blood), histotoxic hypoxia (the presence of a toxin), decompression sickness, or even simply dehydration, lack of sleep, or nervousness, the root cause of the problem is yet to be found.