The F-35 multirole fighter won't be close to ready before 2019, the US House Armed Services Committee was told on Wednesday.

The aircraft, which is supposed to reinvigorate the American military's air power, is suffering numerous problems, largely down to flaws in the F-35's operating system. These include straightforward code crashes, having to reboot the radar every four hours, and serious security holes in the code.

Michael Gilmore, the Pentagon's director of operational test and evaluation, reported that the latest F-35 operating system has 931 open, documented deficiencies, 158 of which are Category 1 – classified as those that could cause death, severe injury, or severe illness.

"The limited and incomplete F-35 cybersecurity testing accomplished to date has nonetheless revealed deficiencies that cannot be ignored," Gilmore said in his testimony [PDF].

"Cybersecurity testing on the next increment of ALIS [Autonomic Logistics Information System] – version 2.0.2 – is planned for this fall, but may need to be delayed because the program may not be able to resolve some key deficiencies and complete content development and fielding as scheduled."

He reported that around 60 per cent of aircraft used for testing were grounded due to software problems. He cited one four-aircraft exercise that had to be cancelled after two of the four aircraft aborted "due to avionics stability problems during startup."

In another exercise, conducted by the Marine Corps in May 2015, the exercise was delayed because file formatting problems meant target information couldn't be uploaded to the aircraft. The US Air Force had similar problems, aborting a test after none of the aircraft could fly due to startup problems requiring software and hardware shutdowns and restarts.

The F-35 is the first modern US military aircraft not to have a heads-up display. Instead, pilots will wear the display as part of their helmet, but the current level of software development means that the helmets can't handle night vision, which leaves pilots at something of a disadvantage.

Mechanical problems also dog the aircraft, he reported, especially with the ejector seat mechanism. Gilmore said that after initial testing, pilots weighing below 136 pounds won't be allowed to fly the aircraft, and there are "serious" problems for those weighing over 165 pounds.

For pilots in the 136-165 pound weight class – that's about 27 per cent of all aviators – the evaluators estimated the probability of death during ejection was 23 per cent, and the probability of "some level of injury resulting from neck extension to be 100 per cent." (General Chris Bogdan claims those figures are wrong, and that the pilots have a 1-in-200,000 chance of neck injury.)

Pentagon officials said [PDF] that the cost of the F-35 program has actually fallen in the last two years by $12.1bn. The full cost for the US government between now and 2038 is down to $379bn, or around $12.7bn annually, for 2,457 aircraft.

The US Department of Defense said it estimates that "the F-35 fleet will cost around $1 trillion to operate and support over its lifetime, which poses significant long-term affordability challenges for the department." ®