Think Los Angeles at rush hour is bad? Try doing it half-blindfolded with nothing but a radio and a few blinking lights to show you the way. That's how pilots navigate the invisible highways in the sky, and there's a beautiful design that makes it all work. It only took about a hundred years to come up with it.
When you take a step back and think about it, airspace design—and the air traffic control system that dictates it—is a small miracle. Actually, it's a pretty big one. This complex set of rules, developed and refined since the early days of aviation, keeps planes from crashing into each other or slamming into the ground when trying to land in bad weather. Incidentally, it was these very kinds of tragedies that prompted authorities to write the rules to begin with before technology took the reins, shaping the way we fly today. In the next ten years, technology will transform it all again, but I'll come back to that. First, let's get our history straight.
It all started back in the 1920s when the most prominent pilots in the United States were actually mailmen. These guys would fly by-planes from coast-to-coast along the original transcontinental airway. (Even Charles Lindbergh got in on that action.) In 1927, having realized the business potential of passenger air travel, the Department of Commerce took control of the airway from the U.S. Postal Service, and the nation's first air traffic control tower opened three years later in Cleveland. Before that, pilots relied on hand signals or flags—even giant arrows—on the ground for signals. Aside from that single superhighway connecting the coasts, though, all of America's airspace remained uncontrolled.
That started to change in the early 30s, when instrument flying became the thing to do. After Jimmy Doolittle's first blind flight in 1929 proved that technology could guide pilots through the skies, the government took a keen interest in regulating air traffic. With backing from the Department of Commerce, which was overseeing aviation at the time, four of the country's top airlines—American, United, Eastern and TWA—opened the first full-blown air traffic control facility to watch over the sky above Newark, New Jersey in 1935. Similar facilities opened in Chicago and Cleveland soon thereafter.
Air traffic control was a pretty manual endeavor in the beginning. Using maps, blackboards, a radio, and mental calculations, the first air traffic controllers kept track of the planes in the air but also began writing the rules that would shape airspace design. To keep planes from colliding midair, this required constant radio contact between pilots and the ground that enabled air traffic controllers to dictate altitude and direction. A control zone that amounted to a five-mile-wide vertical cylinder was set up around airports, and, in 1938, the Civilian Aeronautics Administration (CAA) was formed. Then World War II happened.
The war effort shaped airspace design in many ways, the most profound of which was probably the introduction of radar. Over the next few decades it would become one of the most valuable tools in the control tower as it enabled the air traffic controllers to know the position of aircraft at all time. At around the same time, pilots started relying on ground-based radio beacons to help them navigate, a system that also led to the development of more pronounced airways. For obvious reasons, the web of airways sort of looks like a map of all the Interstate highways. At least in the beginning it did.
As the skies got busier after the war, they also got messier. A series of midair collisions, along with the advent of the jet era, prompted Congress to pass the Federal Aviation Act of 1958. This led to the creation of the Federal Aviation Administration and the beginnings of a more complex system of airways. Below 18,000 feet, there were so-called Victor airways, eight nautical miles-wide each, that were used by both pilots flying under instrument flight rules (IFR) and visual flight rules (VFR). A map of the pathways would resemble a game of connect-the-dots in which each dot was a VHF omnidirectional range (VOR) station that sent beacons up to the planes and helped them navigate.
Above the Victor airways were the jetways. This includes the most restricted airspace, which would later become known as Class A airspace. Air traffic controllers required all pilots to be instrument-rated at these altitudes, although improvements in VOR technology enabled them to map out their own routes independent 0f the established roadways.
But before airspace design became too messy, more rules arrived with the creation of the Department of Transportation in 1967. Air traffic control was also on its way to become more automated thanks to these newfangled machines called computers.
Traffic got worse and worse as the cost of flying dropped, and it effectively went out of control after the airline industry was deregulated in 1978. This created a highly competitive airline industry and also led to the first National Airspace System (NAS) Plan in 1982 that was designed to enhance air traffic control and air navigation to keep pace with the growth of the airline industry over the next 20 years. Efforts to automate the system continued and, soon, the nation's skies resembled an intricate latticework of specialized airways. These stretched laterally across the landscapes below and stacked up in layers, marking different vertical levels of restriction.
The most recent major adjustment to the nation's airspace design arrived in 1993 when the current system of airspace class went into place. This slightly modified version of the international system divided the sky into a veritable layer cake of classes labelled A through G, based on altitude. Whereas Class A represented the strictly regulated jetways, Class G airspace close to the ground was completely uncontrolled. Airspace around busy airports is Class B, while Class C is reserved for airports with moderate traffic, and Class D for airports with very little traffic. Everything else between 1,200 feet and 18,000 feet is Class E airspace.
Today, U.S. airspace is in the middle of yet another redesign. Radar and radio, the very technologies that once drove innovation in the industry, are gradually being phased out as GPS technology takes over. This a potentially transformative development for air traffic control and airspace design as it enables controllers to make minute adjustments that shave minutes or even seconds off of flight time, leading to less congestion both in the skies and on the ground.
It's going to take some time to make the transition, though. Ten years ago, Congress gave the go ahead to the Century of Aviation Reauthorization Act which will usher in a new system for air traffic control—called NextGen—set to launch in 2025. The New York City area stands to benefit the most from these improvements as, with its three airports combined, it has some of the busiest skies in the country. Andrew Blum published a big feature in Wired on the future of New York City's skies back in 2009, detailing how subtle adjustments to airspace design will lead to major improvements in traffic control.
Inevitably, the system's only going to get more complex, and therein lies the challenge. Steve Kelley, a former air traffic controller who's in charge of the FAA's redesign, described the situation succinctly to Wired. "The airspace is the airspace," he said. "No one's going to give us more of it. We just have to use it better."
Images via Aaron Koblin / Century Aviation / FAA / CWAM / Rick Camacho
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A Brief History of Airspace Design