[521] Reserve-fuel requirements are discussed at some length in part 121 of the Federal Air Regulations.^G1 Specific rules for calculating the amount of reserve fuel are given by the Air Transport Association.^G2 The amount of reserve fuel given by these rules is in excess of minimum FAR requirements but is representative of current airline operational practices. The amount of reserve fuel specified by reference G2 depends upon the type of aircraft and the nature of its operation. For example, aircraft in domestic and international operations carry different amounts of reserve fuel, as do supersonic and subsonic transport aircraft. The reserve-fuel rules are also different for propeller-driven aircraft equipped with reciprocating engines and for turbine-powered aircraft.

The reserve-fuel requirements specified by reference G2 for subsonic turbine-powered aircraft employed in domestic and international operations are given as follows:

Domestic Operations

1. Fly for I hour at normal cruise altitude at a fuel flow for end of cruise weight at the speed for 99 percent maximum range.
2. Exercise a missed approach and climbout at the destination airport; fly to and land at an alternate airport 200 nautical miles distant.

[522] International Operations

1. Fly for 10 percent of trip air time at normal cruise altitude at a fuel flow for end of cruise weight at the speed for 99 percent maximum range.
2. Exercise a missed approach and climbout at the destination airport; fly to an alternate airport 200 nautical miles distant.
3. Hold for 30 minutes at alternate airport at 1500 feet altitude.
4. Descend and land at alternate airport.

Flight to Alternate Airport (All Airplanes)

1. Power or thrust setting shall be for 99 percent of maximum subsonic range.
2. Power setting for holding shall be for maximum endurance or the minimum speed for comfortable handling, whichever is greater.
3. Cruise altitude shall be the optimum for best range except that it shall not exceed the altitude where cruise distance equals climb plus descent distance.

^G1 "Certification and Operations: Domestic, Flag, and Supplemental Air Carriers and Commercial Operators of Large Aircraft," FAR Pt. 121, paragraph 121.195 (FAA, June 1974).

^G2 Standard Method of Estimating Comparative Direct Operating Costs of Turbine Powered Transport Airplanes. (Air Transportation Association of America, December 1967).