Two airmen were found dead in a dormitory room at Spangdahlem Air Base in Germany Thursday evening.
In a release Friday, the base said the airmen were found unresponsive at about 6:30 p.m. Emergency responders arrived, but the airmen were pronounced dead at about 6:50 p.m.
Spangdahlem said their names will not be released until 24 hours after their next of kin have been notified.
The F-35s previously took part in the Astral Knight exercise at Aviano Air Base in Italy.
The release said their deaths are now under investigation, and more details will be released later.
Spangdahlem is the home of the 52nd Fighter Wing, which operates F-16 Fighting Falcon fighters trained to perform enemy air defense suppression.