Moving Off FAA Mainframes: The Challenges of Transition - FAA Infrastructure: Air Traffic System History

FAA Infrastructure: Air Traffic System History
Most localized air traffic control systems in use today were designed in the 1960s and '70s and installed throughout those years and into the '90s. Radar has been used since World War II.

Many technologies are used in air traffic control systems. Primary and secondary radar is used to enhance a controller's "situational awareness" within his assigned air space; all types of aircraft send back primary echoes of varying sizes to controllers' screens as radar energy is bounced off their skins. Transponder-equipped aircraft reply to secondary radar interrogations by giving an ID (Mode A), an altitude (Mode C) and/or a unique call sign (Mode S). Certain types of weather also may register on a radar screen.

The traffic-handling systems used at most international airports are highly proprietary. Systems engineers are tight-lipped about them in general. They work hand in hand with the flight-plan system and have many redundancies built into them.

Andy Isaksen, a computer scientist for the FAA in Atlanta, was the designer of the flight-plan system. In a 2005 NetworkWorld article, Isaksen told Deni Connor that the NADIN system's two Philips DS714/81 mainframe computers were originally manufactured in 1968 and upgraded with new processors in 1981. Since then, they have been getting increasingly harder to maintain, support and write code for, Isaksen said.

The Isaksen flight-plan network is the centerpiece of the FAA's air traffic system. Any aircraft that enters or leaves U.S. air space has to file a plan into the system. The network also serves as the sole data interchange between the United States and other nations to distribute flight plans for commercial and general aviation, as well as weather and advisory notices to pilots.

To its credit, the air traffic system probably has been running around the clock 99.9 percent of the time since the tail end of the Reagan administration. But the time has come for it to be replaced, and everybody knows it.