The middle-aged priest climbs 15 flights of stairs, and is not the least bit out of breath.
The taxi drivers make book on when the man will jump. The winner will be the man who has picked the time closest to the jump. When the clocks strike 2:00, the man who has 2:00 says that knocks him out and throws the slip away. But he would not be ruled out until 2:31.
The police are directed to take their equipment to the thirteenth floor. Most buildings, and all hotels, do not have a thirteenth floor. The numbering goes from twelve to fourteen.
At the end of the movie the son of Officer Dunnigan enters through the revolving door in a clockwise, wrong, direction. Officer Dunnigan and he hug and then leave the hotel, exiting through the revolving door, again pushing it in a clockwise, wrong, direction even though all revolving doors turn in a counter-clockwise direction. The push handles are clearly visible on the opposite side of the door.
Stock rear projection footage of normally-moving motor traffic while Cosick is on ledge is not consistent with huge traffic jam shown in area surrounding hotel where he is threatening suicide leap.
In the opening few minutes: The car and trash can in the opening two shots are no less than 4' different; then in the shot a few moments later, looking down from the hotel room window, the car is about 8 feet from the trash can.
The reporter on the street looking up at Cosick on the ledge describes him as about 23 years old. Charlie Dunnigan also refers to him as "boy" when he first looks out the window and talks to him. Richard Basehart was 37 when he made this movie and looked close to 40, not like a boy.