PARIS, June 9 -- The fighter jet was supposed to be the proof. Proof that Europe could build its own sixth-generation warplane, free of American engines and American permission, a flying symbol of the strategic autonomy its leaders have invoked for a decade. On Monday, France and Germany killed it, and the thing that killed it was not Washington, and it was not money. It was the question of whose company would be in charge.

Berlin and Paris formally ended the manned-fighter heart of the Future Combat Air System, the roughly 100-billion-euro program launched in 2017 by Emmanuel Macron and Angela Merkel as Europe's flagship answer to American air dominance. A German official put it bluntly, saying the companies would not be able to come to...