Snowballing Delays In F-35 Development Lead To Increased DOD Risk, GAO Says

The DOD is planning to buy up to 152 F-35 aircraft annually, despite the fact the program remains stalled in operational testing due to holdups in developing the F-35 simulator that is crucial in determining the performance and reliability of the fighter, the GAO said. 

The delay in officially moving into full production, however, hasn't stopped the DOD from buying the aircraft at near full production rates, the GAO said. By the time the F-35 advances from the final development milestone, the DOD will have already acquired about a third of the fighters it intends to buy.

"[I]t means that more aircraft will need to be fixed later if more performance issues are identified, which will cost more than if those issues were resolved before those aircraft were produced," the report said. "At the same time that DOD is purchasing aircraft at these high rates, those that are already in the fleet are not performing as well as expected."

A three-year delay in the F-35 Block 4 modernization schedule aimed at upgrading the fighter's hardware and software systems is also leading to cost overruns, the GAO said. In 2021, Block 4 development costs jumped $741 million in the span of a year, to $15.14 billion, the report said.

The DOD intends to buy 2,470 of the stealth fighters as part of fleet modernization for the U.S. Air Force, Navy, and Marine Corps. To date, more than 700 of the aircraft have been delivered by Lockheed Martin to the U.S. services, and foreign military customers, according to the GAO.

Central to the delay in the program moving from operational test and evaluation to full-rate production phase is the lack of an aircraft simulator, which runs mission systems software and software models to simulate complex scenarios for testing.

"The program office completed the final remaining open-air weapons trial in June 2021 but needs to complete 64 simulated test trials in the simulator before initial operational testing will be finished," the GAO said. "Before DOD can conduct the final 64 simulated test trials, the simulator must be fully developed." Program officials have also not determined when that simulated testing could be completed, it said.