The first person to tackle the terrorist on the train was a Frenchman. He later turned down the Légion d'honneur and asked to remain anonymous because he feared reprisals from other Islamists living in France.
Director Clint Eastwood enlisted the actual Americans who took down the terrorist to play themselves in this movie: Anthony Sadler, Alek Skarlatos, and Spencer Stone.
Roughly eight weeks after the Thalys train attack, Spencer Stone was stabbed in the back several times by James Tran, outside a downtown Sacramento night club. Stone suffered wounds to his lungs, liver and heart, and he had to undergo emergency open heart surgery. In 2017, Tran was found guilty of attempted murder, causing great bodily injury and the use of a deadly weapon and was sentenced to nine years. Stone was quoted in the Sacramento Bee newspaper, saying, "At the end of the day, I forgive the guy. We all make stupid decisions, some dumber than others. I hope he learns from it."
The plot tagline says "3 U.S. Airmen," but only Spencer Stone is in the Air Force. Alek Skarlatos is Army National Guard and Anthony Sadler is a civilian.
At 94 minutes, this has the shortest running time out of all of Clint Eastwood's directorial projects. The previous record holder was "Sully" (2016) at 96 minutes.
Clint Eastwood was attached to direct The Ballad of Richard Jewell since 2014 but dropped out in 2016 to do Impossible Odds as his next directorial project after finishing Sully (2016). The project wasn't ready yet and needed more time in development, meaning that Eastwood needed another project. He decided to sign on to helm this project as his next directorial film.
An image of Clint Eastwood's face from Pale Rider (1985) appears on a character's t-shirt.
While in the medic class, Alex addresses the instructor, a female non-commissioned officer, as "ma'am." NCOs are addresses by their rank, e.g. "Sergeant," "Master Sergeant, etc." Outside of basic training (and then, only in the Marines), they are never addressed as "ma'am" or "sir." Alex has been in the service long enough to know this.
This film marks the first time that Clint Eastwood and DP Tom Stern used Zeiss Master Anamorphic lenses, which have the least anamorphic distortion. Their previous anamorphic shot movies were Filmed in Panavision.
Many of the professional actors in this film are better known as sitcom stars: Tony Hale and Judy Greer were both in Arrested Development, Jenna Fischer in The Office, Thomas Lennon in Reno 911!, and Jaleel White in Family Matters.