The premise is fairly simple: two pilots (played by John Travolta and Christian Slater) of the "B-3 Stealth Bomber" (a fictional iteration on the B-2) run a top secret exercise with a pair of live nuclear bombs ... only one of the pilots has decided he needs a big pay off and sabotages the mission so that he can steal and sell the bombs. The rest of the movie consists of the second pilot and a Utah park ranger (Samantha Mathis) tangling with the other pilot and his crew, trying to stop the sale and/or detonation. "Broken arrow" is a term (fictional or not, I don't know) indicating a lost nuclear weapon.
John Woo (the director) is best known for his gun battles and explosions. And I don't know what was up with Mathis: her acting is off-the-charts awful in this one. Not that it's a great script or anything, but Travolta and Slater have a lot of fun with it. The action is fairly good - over-the-top Woo, but actually slightly more believable than usual. Classic quotes include "I don't know what's scarier, losing nuclear weapons, or that it happens so often there's actually a term for it," and "would you mind not shooting at the thermonuclear weapons?"