F-22 Fighter Jets Face More Pentagon Safety Rules
The Pentagon has issued further safety procedures for its most advanced fighter jet after pilots complained of oxygen shortages during flights.
The rules include limiting the distance F-22 planes can travel from airstrips.
Defence Secretary Leon Panetta did not rule out grounding the jets again if necessary.
The Air Force banned its F-22s from flying for four months last year to investigate the oxygen-deficit problem, but its cause remains unclear.
The Air Force has introduced more than a dozen pilot safety rules in the F-22, and says oxygen issues are very rare, but some pilots have refused to fly the aircraft.
Dizziness and blackouts
The safety precautions announced on Tuesday mean the F-22 will have to abandon long-distance air patrol missions in Alaska, the Pentagon said. The jet has never been used in combat.
The defence secretary has also asked for a back-up oxygen system to be put into the planes, with the first of these due to be installed in December.