The US military has grounded its entire fleet of ten Lockheed-built F-35 fighter jets due to a dual generator failure and oil leak that occurred during a flight test last week.

Lockheed spokesman John Kent said that the AF-4 fighter jet, one of the Air Force variants, had encountered the problem while being tested at Edwards Air Force Base in southern California, US.

“Once the cause is known, the appropriate repairs and improvements will be made before flight operations resume,” he added.

The company is developing three variants of the F-35 joint strike fighter with eight international partners to replace over 13 different planes being operated by the US Air Force, Navy, Marine Corps and foreign militaries.

The warplane, being developed with multiple redundancies, has an integrated power package which acts as a starter, air conditioner and back-up power generator, according to Reuters.