The real world: Controllers and technicians warn of a system stretched to its limits, citing mounting delays, overcrowded radio bands, and a rising number of near-misses

The two airliners ¿ a United Airlines DC-4 and a Trans World Airlines Constellation ¿ left Los Angeles international Airport under air traffic control on June 30, 1956, heading east. They cleared the terminal area routinely, but collided over the Grand Canyon. There was no nationwide system of real-time air traffic control in those days.