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Meanwhile, despite repeated, costly modernization efforts, the outdated, overloaded air traffic control system is straining to keep up. Again and again, aircraft simply “disappear” from controllers’ radar screens; last year, Air Force One vanished twice. To compensate for such lapses, controllers must increase safety margins by boosting separation distances and holding planes back. That has kept the accident rate in U.S. commercial aviation stunningly low. But according to the man often called “the father of free flight,” pilot-turned-airline-manager William B. Cotton of United Airlines, that record comes at a price: “Safety has always been maintained at the expense of capacity and efficiency.”

Although the system is straining to the breaking point, it is still remarkable that it works as well as it does, given the way it’s grown. For 40 years, functions, hardware and software have been mixed, matched, replaced and added in, forming a massive patchwork.

Today, controllers guide pilots verbally through each turn, climb, descent, acceleration and deceleration-from takeoff to landing-using only radar tracking and radio communications. Each controller in the FAA’s en-route centers monitors a sector that may be several hundred kilometers wide, with as many as 20 planes crossing at a time.

Limiting planes to preset routes across each sector helps the controller track and negotiate traffic. This is critical, because controllers must perform time-and-distance calculations in their heads. But preset routes add turns and miles, wasting fuel. And “handing off” flights from one controller’s sector to another’s creates opportunities for potentially dangerous errors, and for delay-inducing logjams when volumes climb (as they have recently with the surge in short-haul regional jet operations).

Even when this system was new, a few upstart innovators were thinking about making it better. Among the first was Cotton, now United Airlines’ Air Traffic and Flight Systems manager. In 1965, in his MIT master’s thesis, Cotton proposed that, instead of relying on ground instructions, planes could maintain flight separation through automatic air-to-air communication, with cockpit displays of the data they exchanged. At the time this scheme was a dream, since the technology to implement it didn’t exist. More than three decades later, these ideas would become essential elements of the FAA’s own free-flight concepts.

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