For Part 121 Operations, a Certificate Holder May Use a Regular, Refueling, or Provisional Airport. For part 121 operations, a certificate holder may use any regular, refueling,or provisional airport as an alternate airport, provided the airport is authorized for the type of aircraft being used. There is no need to dually（双重） designate an airport as an alternate for a particular aircraft type, if that airport is already authorized as a regular, provisional, or refueling airport for that aircraft type.
§125.1 Applicability. (a) ….this part prescribes rules governing the operations of U.S.-registered civil airplanes which have a seating configuration of 20 or more passengers or a maximum payload capacity of 6,000 pounds or more when common carriage is not involved.
然后对于“common carriage is not involved ”的解释是§110.2
§110.2 Definitions When common carriage is not involved or operations not involving common carriage means any of the following: (1) Noncommon carriage. (2) Operations in which persons or cargo are transported without compensation or hire. (3) Operations not involving the transportation of persons or cargo. (4) Private carriage.
最早的AC25-7的TAKEOFF AND TAKEOFF SPEEDS章节用来解释25.107的这一条当中，说明：
(7) section 25.107(f) – Liftoff Speed – The liftoff speed (VLoF) is defined as the calibrated airspee at which the airplane first becomes airborne, i.e., no contact with the runway. This allows comparison of liftoff speed with tire limit speed.
The maximum ground speed at liftoff, considering the entire takeoff operating envelope and taking into account 50 percent of the headwind and 150 percent of the tailwind, in accordance with § 25.105(d)(1), must not exceed the tire speed rating established under § 25.733(a) or (c).