
In 1961, the U.S. decided to create a program where they would have nuclear weapons in the air 24/7 in order to be prepared to respond to any potential attack. But instead they ended up dropping a bomb on their own country.
Sources:
https://www.bbc.com/reel/video/p0c5889f/broken-arrows-the-accidents-that-could-end-the-world
https://en.wikipedia.org/wiki/Nuclear_arms_race
https://www.atomicarchive.com/almanac/broken-arrows/index.html#1960