That must vary by theater, or perhaps practices change from time to time. My brother worked at a movie theater in high school (20 years ago), and the theater he

That must vary by theater, or perhaps practices change from time to time. My brother worked at a movie theater in high school (20 years ago), and the theater he worked would not play movies if nobody had bought a ticket. He told me they would occasionally catch people trying to sneak free movies that way - the projectionist would notice someone in the theater for a time which was going to be canceled, call the box office to confirm if they had sold a ticket, and if not they would get a manager to escort the person out.