The U.S. Air Force's F-35A Lightning II appears to be unable to fly as far as once predicted, according to a Pentagon document.
The aircraft is currently estimated to have a combat mission radius of 584 nautical miles, just short of the required 590 nautical miles, according to a Selected Acquisition Report dated Dec. 31.
Program officials had previously estimated that the aircraft, unrefueled, would be able to strike targets 690 nautical miles away.
The report says the shortfall is caused by increased use of engine bleed air and fuel capacity issues "that are not yet fully known."
"This estimate is based on preliminary data," the report reads, and more testing will reveal whether it is close to the truth.
The report says the range estimates have also been cut for the Marine Corps' short take-off B-model and the Navy's carrier-base C-model. But those planes' ranges still exceed the requirements.
The B-model has a radius of 469 nautical miles and a requirement of 450; the C-model, 615 and 600.