GAO Report on F-35 Modernization

May 17, 2024 11:47 AM

The following is the May 16, 2024, Government Accountability Office report, F-35 Joint Strike Fighter: Program Continues to Encounter Production Issues and Modernization Delays

From the report

What GAO Found

The F-35 program achieved full-rate production in March 2024. Full-rate production is the point when a program has demonstrated an acceptable level of performance and reliability. Further, the F-35 program completed development of its testing simulator and conducted its final simulated tests.

Even with this progress, the F-35’s contractors continue to deliver the engines and aircraft late—a trend that worsened in the last few years. According to program officials, late deliveries were partially caused by manufacturing issues and parts shortages. The program and contractors are mitigating these issues.

Percentage of Engines and Aircraft that Contractors Delivered Late in Calendar Year 2023 Contractor

Parts delivered

Percentage delivered late

Pratt & Whitney



Lockheed Martin



The program also has not yet determined how to modernize the thermal management subsystems that provide cooling to the aircraft. These efforts continue to face risks due to undefined requirements, immature technologies, and varying cost estimates. GAO has made recommendations to address these risks, which the program has not yet fully implemented.

Why GAO Did This Study

After over 20 years, the F-35 Lightning II Joint Strike Fighter program—the Department of Defense’s (DOD) most expensive weapon system program— completed its baseline development phase and moved into full-rate production. DOD is in its sixth year of a hardware and software modernization effort known as Block 4 and is considering other modernization efforts. DOD estimates that these development efforts—as well as the costs to maintain and operate the 2,470 planned aircraft through 2088— will exceed $2 trillion.

Congress included provisions in statute for GAO to review the F-35 program. This report assesses the program’s: (1) progress and risks as it approached full-rate production; (2) progress in modernizing the aircraft’s capabilities; and (3) progress in upgrading the engine and other subsystems.

GAO collected and analyzed cost, schedule, and production data; reviewed relevant program documentation; and interviewed DOD officials and contractor representatives.

What GAO Recommends

GAO has reviewed the F-35 program annually since 2001 and made 54 recommendations for improvement. In May 2023, GAO made seven recommendations aimed at improving Block 4 cost reporting and the program’s modernization efforts (GAO- 23-106047). DOD has taken action to address some, but not all, of GAO’s recommendations.

Download the document here.

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