The production was shot in 22 days and Mel Gibson himself expressed he was surprised when the final running time clocked in at merely 91 minutes, making this his shortest-directed film.
121.5 is a real frequency for emergencies. This is accurately portrayed in the movie.
It was Mark Wahlberg's idea to have the pilot be bald. The filmmakers acknowledged his appearance strongly mirrored that of the BTK killer Dennis Rader.
According to Mel Gibson, Mark Wahlberg improvised much of his character's dialogue, explaining, "Mark's got a good dark side he takes stuff from. Every now and again he'd let it out and I can't even repeat some of the stuff he'd say, in fact we had to cut most of it out, it was like REALLY sick- but we hint at it."