The air traffic control system is a crucial part of keeping our skies safe, organized, and efficient in an era of ever increasing congestion. It began as a way to give pilots essential information about weather and traffic at the first airports. People on the ground used any technology they could to communicate with pilots, whether by waving flags, flashing lights, or by using radio.

In its early days, aviation was extremely dangerous. Every flight was a gamble and a risk. But the number of people flying increased, so did accidents and fatalities, and thus illustrated the need to not only provide pilots with information but also to tell them what to do.

This was especially true in the late 1920s and early 30s, where commercial aviation was becoming more and more commonplace. The first air traffic controllers worked as tower controllers for private companies (usually airlines) at each airport, who provided landing and takeoff clearances to arriving and departing aircraft. With no enroute ATC, aircraft experienced congestion, near misses, and midair collisions, especially in bad weather.

Early airfields had towers with rotating light beacons to help pilots navigate visually. This tower also had a windsock. Image via FAA.

Pictured is Sergeant William P. Bostic of the 301st Fighter Squadron (the Tuskegee Airmen) in a control tower. At this point, light guns were still being used to signal pilots, as well as radio communications. Image via Library of Congress.

Although formal ATC procedures were first introduced at ICAN, the precursor to ICAO, in 1922, the US ATC system was taken over by the government in 1936. The first Air Route Traffic Control Centers (ARTCC) were opened in 1936, starting with Newark, NJ, Chicago, IL, and Cleveland, OH. They employed simple yet effective technologies, the most crucial of which was radio, which not only allowed communication but also navigation by sending directed beams through the air for pilots to follow. At this point, tower controllers were still employed privately, although the government also took over them in 1938.

Then, World War II happened, which created leaps and bounds of progress for ATC. Because WWII created a significant need for cargo transport, the commercial aviation industry grew quickly. Additionally, advances in military aviation technology were well adapted to civilian practices. Most notably, the invention of radar and application in ATC was revolutionary. Instead of just guessing and predicting the location of aircraft based on pilot position reports, controllers could actually see all aircraft on screen in real time, vastly improving the safety of the system.

Initially, radar was only used by tower controllers near airports, as the government feared the high costs associated with implementing it over larger areas. This continued until 1956, when a midair collision over the Grand Canyon killed 128 people. The government quickly took action to improve the national ATC system, which included expanded radar coverage.

In the 80s and 90s, the FAA was plagued by an overarching issue: they were behind the times. Like most other industries, automation was inevitable, and it created new jobs while removing obsolete ones. But advances in technology were necessary for automation to be successful or even feasible. The introduction of the computer into the ATC system was a huge leap forward, yet it was still lacking in many aspects. The FAA made several attempts at introducing automation in the ATC system, but it was almost always held back by a fear of increased cost. In particular, controllers were (and still are) relying on paper flight strips to keep track of critical information about flights and their progress. The FAA had pushed for replacing paper with electronic flight strips, but kept seeing different obstacles, and today, paper strips are still being used. Vacuum tubes were another example of the FAA being stuck in the past. A vacuum tube was a piece of technology developed early in the 20th century that was a precursor to the transistor, a cornerstone of modern electronics. Though they had become largely obsolete by the 90s, the FAA was still buying them in bulk to be used in outdated ATC technology.

An example of a vacuum tube. Image by Mataresephotos via Wikimedia Commons, CC BY 3.0.