USAF Grounds 55 F-35 Fighter Jets Over Oxygen Problems

The US Air Force has grounded 55 F-35 Joint Strike Fighter jets at Arizona airbase for the second time after pilots again observed oxygen deprivation during flight tests.

Pilots at the Luke Air Force base in the US state of Arizona noticed that they were becoming deprived of oxygen during flight tests, experiencing what the branch described as "physiological incidents while flying", according to a new report from Defense One Saturday.

This is the second grounding since F-35s were declared ready for service by the US Air Force last year, after embedded electrical lines inside of the aircraft's fuel tanks were found to have cracking insulation, the report says.

However, a US Air Force spokesperson was quoted as saying that the Virginia-based F-35 program head office has now implemented a "formal action team of engineers, maintainers and aeromedical specialists to examine the incidents to better understand the issue".

The Arizona F-35s are anticipated to be cleared to fly on Monday, it says.