Air Force Capt. Andrew “Dojo” Olson, commander of the F-35 Demonstration Team, performs a high-speed pass during the Oregon International Airshow in McMinnville, Ore., Sept. 21, 2019.

Air Force Capt. Andrew “Dojo” Olson, commander of the F-35 Demonstration Team, performs a high-speed pass during the Oregon International Airshow in McMinnville, Ore., Sept. 21, 2019. U.S. Air Force / Senior Airman Alexander Cook

F-35 Costs Still Climbing, as Pentagon Updates the Fleet

New GAO report details another $1.4 billion in upgrade costs, and additional delays.

The U.S. military's costliest weapons program keeps getting more expensive: upgrades for the F-35 fleet will add more than $1 billion to last year's estimates, according to a new Government Accountability Office report.

The Pentagon is five years into updating its fleet of F-35s, an effort known as Block 4. But the cost of the upgrades continues to climb, with an increase of $1.4 billion since GAO’s April 2022 report, bringing the total cost to $16.5 billion. 

“The total increase to date is 55 percent more than what the program originally reported it would cost in 2018,” the government watchdog agency said.

And before the F-35 fleet can receive the upgrades, it needs a suite of hardware and software improvements, known as Technology Refresh 3, or TR-3. Those improvements are a year behind schedule and won’t be delivered until April 2024.

The first TR-3 flight test flew in January—an “important milestone” but one that uncovered software problems that “the contractor did not identify in software labs,” GAO said.

The new issues mean the program will have a tight timeline to complete additional tests and fix the software problems, GAO said, since TR-3 is supposed to be delivered with the first Lot 15 aircraft in July. 

The F-35’s current Pratt & Whitney engine is also driving up program costs, because it’s running twice as hot as it was designed to, requiring earlier and more frequent aircraft maintenance. The extra heat could add up to $38 billion in maintenance costs to the program in the coming decades, GAO said.

However, the F-35 Joint Program Office said it is “already very confident” it can reduce the $38 billion figure by upgrading the existing Pratt engines through a program called engine core upgrade, or ECU. The Air Force recently decided that it would not pursue a new, adaptive engine for its F-35 fleet. 

The Pentagon could not immediately disclose how much the upgrade would drive down the $38 billion figure. 

“The ECU will restore engine life, and the [power and thermal management system] solution will ensure that the air vehicle can support future capability growth,” JPO said in a statement. 

While JPO knows the current engine doesn’t have enough power, it doesn’t know how much more power it will actually need. The Pentagon isn’t sure what the “high-end margin” of power should be for the fighter, F-35 Program Executive Officer Lt. Gen. Michael Schmidt said in March.

JPO has compared engine upgrade options, but “it has not fully defined the power and cooling requirements the engine and related components will need to support capabilities beyond those planned through 2035,” GAO said.

The program also continues to struggle with aircraft and engine delivery delays, GAO said. 

“In 2022, Lockheed Martin delivered 50 percent of aircraft late, which represents the highest level of late deliveries over the past 6 years and three times worse than the percentage in 2021,” the office said.

As for the engines, Pratt only delivered four of 127 F135 engines on time in 2022, “even with multiyear efforts to address this long-standing issue,” GAO said. 

The program had relied on a stockpile of engines, a “standing inventory of engines at government facilities,” to mitigate late deliveries, GAO said, but after an F-35B crashed in December and engine deliveries were paused because the Pentagon found a vibration in the F135 engine, the stockpile is gone and there is no longer a “buffer.” 

Engine deliveries from Pratt resumed in February, and program officials told GAO they are working on a “recovery plan” to restore the stockpile.