[3] The JSF program was the result of the merger of the Common Affordable Lightweight Fighter (CALF) and Joint Advanced Strike Technology (JAST) projects.

[6] The CALF was a DARPA program to develop a STOVL strike fighter (SSF), originally under the Advanced Short Takeoff and Vertical Landing (ASTOVL) project, for the United States Marine Corps and replacement for the F-16 Fighting Falcon.

CALF project was chosen after Paul Bevilaqua persuaded the Air Force that his team's concept (if stripped of its lift system) had potential as a complement to the F-22 Raptor.

This investment allowed Canada to participate in the extensive and rigorous competitive process where Boeing and Lockheed Martin developed and competed their prototype aircraft.

[15] Arguably the most persuasive demonstration of the X-35's capability was the final qualifying Joint Strike Fighter flight trials, in which the X-35B STOVL aircraft took off in less than 500 feet (150 m), went supersonic, and landed vertically – a feat that Boeing's entry was unable to achieve.

One of the main reasons for this choice appears to have been the method of achieving STOVL flight, with the Department of Defense judging that the higher performance lift fan system was worth the extra risk.

[16] The United States Department of Defense officials and William Bach, the UK Minister of Defence Procurement, said the X-35 consistently outperformed the X-32, although both met or exceeded requirements.

In July 2019 United States removed Turkey from the Joint Strike Fighter program, following the country's acquisition of the Russian S-400 missile system.

[19] In April 2009, the Wall Street Journal reported that computer spies, allegedly Chinese but acknowledged to be from uncertain sources, had penetrated the database and acquired terabytes of secret information about the fighter, possibly compromising its future effectiveness.

[27] On 11 March 2010, United States Senate Committee on Armed Services investigated the progress of the JSF program in a meeting with Pentagon officials, emphasizing cost due to the risk of a Nunn-McCurdy process.

[31][32] Concerns about the F-35's performance have resulted partially from reports of simulations by RAND Corporation in which three regiments of Chinese Sukhoi Su-27 fighters defeat six F-22s by denying tanker refueling.