According to reports, the F-35 program is currently undergoing a modernization project called Block 4, and we have found that the international community often needs toAnalysis of Reasons for F35 Delayed DeliveryBecause the US Department of Defense provides capabilities to combat personnel by gradually developing, testing, and delivering a small batch of capabilities every six months. This process, known as C2D2, is based on the agile software development process. However, the US Government Accountability Office stated that the remaining development plan for Block 4 cannot be realized. The Ministry of National Defense has been working on modernizing Block 4 for three years and continues to expand its timeline and budget. For example, in 2018, the Department of Defense reported that the development of Block 4 would cost $10.6 billion between fiscal years 2018 and 2024, "the report stated. As of September 2020, the Department of Defense reported to Congress that all Block 4 costs are expected to exceed $14 billion, covering the fiscal years 2013 to 2027. The GAO team found that the given schedule estimate was based on estimates made at the start of the work, rather than on contractor performance.

The report found that there were delays in the development of the F-35 joint simulation environment for running mission system software and other software models, which prevented the project from completing 64 planned tests in 2020. These issues were discovered in August 2020, and there is currently no timeline for resolving them. It is reported that the reason for the delay of simulator production is related to the serious overall opening defects, production delay and quality problems, the efforts made to solve the problem of Türkiye's withdrawal from the supply chain, and the aircraft's failure to meet the reliability and maintainability goals. The delay of simulator production has further delayed the full production since March this year. It is reported that despite these issues, the project is still able to conduct 4 outdoor tests, 2 out of 3 missile tests, and combat network security tests in the Mugu Cape sea area. It is reported that Technology Update 3 (TR-3) is a set of software and hardware technologies that provide aircraft with updated processing capabilities, display units, and increased memory. It is expected to be deployed on the 15th batch of aircraft in 2023. The report also found that the Block4 software development of the plan did not follow leading practices. The report states that Lockheed Martin is unable to use automated tools to obtain real-time performance data, thereby making its collected software development metrics helpful. The report found that the project also requires performance targets for software metrics. The report states, "Although we recognize the challenges of transitioning to agile development, after three years of effort, the F-35 program still faces issues in effectively implementing the C2D2 approach to develop and deliver Block 4 capabilities. The aircraft contractor continues to delay the delivery of capabilities, and the remaining schedule contains significant risks that cannot be achieved based on past performance speed. Although the procurement project office is committed to providing capabilities to combat personnel faster, the procurement project has not yet achieved its initial iteration plan. If there is no achievable schedule based on historical performance, the project is likely to continue to be lower than expected, and combat personnel will have to wait longer for promised capabilities