The situation with the TR-3 software upgrade remained unresolved throughout last year. Reports now suggest that efforts to upgrade the aircraft have "reached a dead end." In 2025, no new combat capabilities were delivered. At the same time, F-35 aircraft conducting combat missions in the Middle East are still equipped with the earlier TR-2 software version.
According to Bloomberg, this information comes from the annual report of the Pentagon's testing authority, the Office of the Director, Operational Test and Evaluation. The report states that the TR-3 upgrade was largely unusable for most of last year due to stability issues and capability shortfalls. These problems remained unresolved at least as of September 30.
Read more: Europe Continues F-35 Orders Despite Critical U.S. Dependence Concerns
"The F-35 program continues to demonstrate a lack of improvement in meeting schedule and performance goals for software development and testing, failing to meet expectations set by its agile development methodology," the report states. It also notes that the process of fixing deficiencies and integrating new capabilities has effectively stalled.
In addition, concerns were raised that the F-35 completed only three out of nine planned cyber vulnerability tests last year. Even in those three tests, "additional deficiencies" were identified. The remaining tests are expected to be completed this year.
The TR-3 software upgrade is a central component of the broader Block 4 modernization effort. Problems with TR-3 first emerged in 2023, and since then deliveries of aircraft equipped with this upgrade have been repeatedly delayed. At one point, Lockheed Martin was forced to store a significant number of completed F-35s while attempting to resolve these issues.
The company eventually introduced an interim version of the upgrade as a compromise. In July last year, after months of delays, 72 F-35 aircraft were delivered to the U.S. military. However, the United States Department of Defense withheld final payments until the TR-3 upgrade demonstrates full functionality in both training and combat missions.
More broadly, the Block 4 modernization is now expected to focus on capabilities that the F-35 can realistically achieve within at least five years, around 2031, even though completion had originally been planned for this year.
Earlier, Defense Express reported that Switzerland has finalized the number of F-35 aircraft it plans to acquire, but will have to pay an additional $505 million while purchasing six fewer jets.
Read more: UK Defense Intelligence: Typhoon and F-35 Jets Fly First Air Defense Patrols over Bahrain, Defend Qatar, Cyprus, UAE and Jordan, Drones Shot Down After Iraq Base Attacks, 400 Air Defense Personnel Deployed
