Tom Cruise is notorious (or famous?) for doing his own stunts in films, but even this stunt is a bit extreme for his standards. Via io9:
The high altitude, low opening (HALO) jump is a means of airdropping military personnel into hostile territory undetected, developed in the 1960s by the United States Air Force. It’s a normal sort of thing to appear in a spy movie. What’s less normal—unheard of, actually—is for an actor to perform the unusually dangerous feat. So, of course, Tom Cruise had to do it.
While Cruise is famous for doing his own stunts, this one is ridiculous even by Cruise’s standards. The normal HALO jump occurs at between 15,000 and 35,000 feet—that’s an average of five miles straight up—and requires specialized equipment and substantial training, lest the jumper suffer from the bends or hypoxia. It is not something normal people can even attempt. For comparison, normal skydiving occurs at around 13,000 feet.
To film a Mission: Impossible—Fallout HALO sequence, Cruise performed the maneuver several times, as outlined in a video recently released by Paramount Pictures. In order to film the sequence, which had to take place at sunset, the 55-year-old man jumped out of cargo planes during the three-minute window necessary to get the lighting right alongside a cameraman, with whom Cruise had to position himself in midair, all while managing to survive and succeed at one of the most dangerous things a person can possibly do.