Pentagon Reports F-35 Block 4 Upgrades Delayed Until 2031 Amid Cost Overruns

The F-35 program faces significant delays and cost overruns, with the Block 4 modernization now expected to be completed no earlier than 2031, five years behind the original schedule. The Government Accountability Office (GAO) reports that the program has reduced the scope of Block 4, cutting some capabilities and deferring others, particularly those dependent on an engine upgrade that will not be produced until 2031. Despite efforts to incentivize timely deliveries, Lockheed Martin and Pratt & Whitney have continued to deliver aircraft and engines late, with an average delay of 238 days in 2024. The program has paid hundreds of millions in incentive fees, but existing structures allowed contractors to receive payments despite late deliveries, prompting calls for reevaluation of these incentives. The F-35 remains critical to U.S. national defense and allies, and program officials believe the revised Block 4 plan can meet new cost, schedule, and performance targets more predictably. The Pentagon is reorganizing modernization efforts into a new subprogram to improve execution, aiming to accelerate capability delivery despite ongoing challenges.