In July 2019, the Pentagon kicked Turkey out of the F-35 fighter jet program, ending Turkish factory work on some components of the next-generation fighter jet and canceling Turkey’s multibillion-dollar purchase of several dozen of the planes. The decision, a result of Turkey’s purchase of S-400 anti-aircraft missiles from Russia, exacerbated an already deep crisis of confidence between Ankara and Washington.

U.S. and NATO officials questioned the motives and judgment of Turkish President Recep Tayyip Erdogan. The S-400 was not only a financial boon for NATO’s prime adversary, but the Russian system could track and gather intelligence on the F-35 capabilities and enhance the Russian ability to counter an aircraft the Pentagon planned to rely upon for decades.