WASHINGTON • The United States military's futuristic F-35 fighter jet remains dogged by dangerous problems that are sure to further complicate what is already the most expensive weapons project in history, a Pentagon report says.
The plane, which boasts a version that can take off and land vertically, is supposed to form the backbone of the military's future fighter fleet, ensuring US dominance in the skies for years to come with radar-evading technology.
The military has already taken delivery of dozens of the planes, but new batches continue to be refined and tested.
In the latest blow to the programme, engineers uncovered a slew of flaws during extensive testing of the newest versions of the F-35 Joint Strike Fighter, the Pentagon report found, adding to a litany of issues including software bugs, technical glitches and cost overruns.
Perhaps the most damning section of the report, released on Monday, is an investigation into the F-35's eject system. Engineers found that pilots who weighed less than 62kg risked being killed by it.
"Testing showed that the ejection seat rotates backwards after ejection. This results in the pilot's neck becoming extended, as the head moves behind the shoulders in a 'chin up' position," the report states.
It also revealed that "deficiencies and limited combat capability" were found in one version of the stealth fighter made for the US Marine Corps. And a US Air Force variant had "inherited deficiencies", the report states, noting that the issues could delay the F-35's release date for the air force past the scheduled year-end deadline.
The Pentagon has budgeted nearly US$400 billion (S$566 billion) for a total of 2,443 F-35 aircraft.
Nine international partners, including Britain, Canada and Turkey, are helping to pay for the jet's development. They are also buying hundreds more of the jet, which is manufactured by Lockheed Martin.
But the programme has faced numerous setbacks, including a mysterious engine fire in 2014 that led commanders to ground planes until the problem could be resolved.