Some airports that are certificated under Part 139 also serve air carrier operations conducted in helicopters. Under the revised Part 139, an airport operator is not required to comply with Part 139 requirements during air carrier operations conducted in a helicopter that would otherwise meet the definition of covered air carrier operations under § 139.1(a)(1).

The word "aircraft" is used in revised § 139.1(a) because it is specified in the authorizing statute (Title 49, United States Code (U.S.C.) § 44706). Since the definition of aircraft in 14 CFR Part 1 includes helicopters, the FAA added § 139.1(c)(5) to clarify that Part 139 does not apply to heliports (see Heliports section of Airports Affected). Revised Part 139.5 defines "heliport" as an airport, or an area of an airport, used or intended to be used for the landing and takeoff of helicopters.

Even though airport operators are not required to comply with Part 139 requirements during air carrier operations conducted in helicopter, many operators of Part 139 certificated airports voluntarily do so because they already comply with Part 139 requirements on a continuous basis, regardless of the number of passenger seats. At such airports, varying types of air carrier operations occur throughout a 24-hour period, and airport operators find it more convenient and economical to comply with Part 139 requirements at all times.