Steve McQueen had a stand up row with wardrobe mistress Wyn Keely after a blouse worn by Shirley Ann field didn't rip during their kissing scene on the first take.
Mike Reilly drowned after parachuting from 2000 feet into the English Channel, near Newhaven, during the filming of a stunt for the film. He was 29 years old, had more than 300 jumps, was British parachute champion and the first Chairman of the newly formed British Parachute Association.
The film utilizes an oft-used storyline of the war movie genre which has two soldiers in love with the same girl.
The last names of the main characters in the film were slightly different from the John Hersey novel. In the novel, "Buzz" Rickson's last name was Marrow, and "Bo's" was Bowman, not Boland.
The scene where the B-17 pilot Woodman brings his aircraft in for a wheels-up landing, and navigator Marty Lynch is killed, comes from the film Twelve O'Clock High.
Three Boeing B-17 Flying Fortresses, restored to flying condition in World War II configurations, were used during filming. Clever camera work and multiple shots of the planes with different names painted on their noses were mixed with wartime footage to create the illusion of an entire Group of B-17 bombers. Noted aviation author and pilot Martin Caidin, who helped fly one of the B-17s from America to England, chronicled the restorations of the aircraft, their flight across the Atlantic, and their use in the film in his book "Everything But The Flak."
Warren Beatty turned down the lead role.