While trying to get sponsors for this series the producers approached the Volkswagen executives and showed them the pilot show which featured actual bombing footage from the war. During the film one of the executives recognized the plant that was being bombed as the VW plant which had made cars for the German army at the time. He commented, "There goes our plant", and the executives then and there decided not to sponsor the show.
The meaning of this series' title '12 O'Clock High' is that of an example of a pilot's enemy position call. Allied pilots during World War II would vocally call-out the positions of enemy airplanes by referring to their bearings via the use of a pretend face of a clock. As such, in this case, 12 O'Clock meant the enemy was directly ahead, whereas 6 O'Clock would mean directly behind. "High" or "Low" referred to whether the enemy was above or below the airplane respectively. "Even" meant that the enemy was level with the pilot's plane.
In the initial episodes of the series, Savage wears a normal A-2 leather flight jacket with rounded collar points and general's stars on the ends of the epaulet straps at the shoulder. This changes in later episodes to another jacket with sharp collar points, stars in the middle of the epaulets, a cigarette pouch on the left arm, and expansion gussets at the rear of each shoulder.
Based on the real life 306th Bomb Group. The fictional 918th was devised by taking 306 and multiplying by three. The fictional name of the base was Archbury, based on the real life Alconbury, the wartime home of the 306th Bomb Group.
B-17s were designed to fly at high altitudes. Flying above 10,000 feet required the crews to wear heated flight suits, gloves, and oxygen. At 20,000 feet it is -70 degrees below zero Fahrenheit. Without the protective clothing frostbite was a certainty. Without oxygen, unconsciousness followed by death was the outcome. Throughout the series, no one is using theirs oxygen mask when on a mission. Some aren't wearing gloves.
As Robert Lansing proved difficult to work with, his character was killed off in the second season premiere. He was replaced by Paul Burke, who had been a guest star in two episodes of season one, including the pilot.