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Free FlightFree Flight

Free Flight

This topic sheet explains "free flight," who it benefits and what it involves. Sources used and places to find additional information are listed at the end of this topic sheet.

"Free flight" is an evolving system that allows pilots to fly more direct IFR routes, at altitudes of their choosing, with minimal ATC interference. So far, the FAA has authorized free flight only at or above 33,000 feet msl (Flight Level 330) in most of the country, FL310 in the western United States. AOPA advocates lowering the free flight floor to FL180 so more general aviation pilots can enjoy fuel and time savings.

Free flight uses GPS, datalink and new cockpit displays to show pilots nearby traffic. ATC intervenes only if two aircraft get too close to each other. A simulation of enroute traffic done by the advisory group RTCA (formerly Radio Technical Commission for Aeronautics) compared the threat of midair collisions between aircraft following VOR airways with those allowed to choose their own routes and altitudes and found slightly fewer enroute conflicts under free flight.

Free flight goes back to 1979, when the FAA proposed loosening rigid ATC restrictions that help cause delays enroute. In early 1981, a limited six-month test was done with Delta, Pan Am, and Eastern flights. Results were encouraging, but the controller's strike on October 16, 1981, brought a halt to the test.

Both time and fuel savings by avoiding dogleg VOR routes accounts for the popularity of free flight. Delta estimated in 1994 that free flight saved about 2 nautical miles per trip; nationwide, the FAA estimated airline fuel savings of some $40 million in 1994, and a NASA study projects airline fuel savings of $1.47 billion per year by 2005. Some experts see free flight giving ATC enough flexibility to handle projected air traffic for the next 50 years.

As free flight evolves, ATC's role will become more monitoring and less hands-on control, with fewer strict route and altitude clearances. A large electronic "alert" area surrounds each aircraft, with a smaller "protected" zone in the immediate vicinity of the aircraft. The size of both zones depends on speed and performance, with faster and higher performance aircraft having larger zones. Only if alert zones touch will ATC intervene, with headings or other instructions to avoid a collision. The smaller protected zone around each aircraft must never touch. Controllers will also help pilots avoid special-use airspace.

Free flight is not a panacea, even as the system becomes more efficient. Experts see it developing as a "continuum of control," depending on how crowded the airspace. For example, departure of an Airborne Express Boeing 727 from its rural Alliance, Ohio, base at 3 a.m. would allow the most free flight, while a rush-hour 6 p.m. arrival at LAX would require the most traditional route, time, and altitude assignments and strict ATC control.

RTCA has issued three reports on free flight, including "GNSS Transition and Implementation Strategy" in 1992, "The Transition to Digital Communications: Urgent Needs, Practical Means," in 1993, and the report of the RTCA Select Committee on Free Flight in January 1995. The last report has 46 recommendations for improving use of free flight, and the FAA has said it hopes to complete these recommendations by 2010. Condensed, the recommendations are:

  • Make full use of GPS capability in removing traditional route restrictions below FL290.
  • Transfer as much conflict resolution as possible from controllers to pilots, using datalink and other advanced technology.
  • Improve controller and cockpit software and hardware to make separation easier.
  • Improve forecasts of thunderstorms, because severe weather plays havoc with routings.

Resources, Additional Help

The following articles were used in developing this topic sheet:

  • Les Blattner, "Free Flight: The Possible Dream?" Air Line Pilot, January 1996, p. 32.
  • Phil Boyer, "President's Position," AOPA Pilot, May 1995, p. 2.
  • Bruce D. Nordwell, "Free Flight: ATC Model for the Next 50 Years," Aviation Week and Space Technology, July 31, 1995, p. 38.
  • Charles Spence, "As Free Flight Encroaches Airspace They Monitor, Air Traffic Controllers Cry Foul," General Aviation News and Flyer, December 8, 1995, p. 6.
  • Official FAA information about free flight is available on the World Wide Web.

And, of course, you can always call AOPA experts for help or advice with any aeronautical problem:

AOPA Pilot Information Center
800/USA-AOPA
(800/872-2672)