via HACKADAY: The First Gui? Volscan Controls the Air

In the 1950s,  computers were, for the most part, ponderous machines. But one machine offered a glimpse of the future. The Volscan was probably the first real air traffic computer designed to handle high volumes of military aircraft operations. It used a light gun that looked more like a soldering gun than a computer input device. There isn’t much data about Volscan, but it appears to have been before its time, and had arguably the first GUI on a computer system ever.

The Air Force had a problem. The new — in the 1950s — jets needed long landing approaches and timely landings since they burned more fuel at lower altitudes. According to the Air Force, they could land 40 planes in an hour, but they needed to be able to do 120 planes an hour. The Whirlwind computer had proven that computers could process radar data — although Whirlwind was getting the data over phone lines from a distance. So the Air Force’s Cambridge Research Center started working on a computerized system to land planes called Volscan, later known as AN/GSN-3.