Pub. L. 86-682, tit. 39, pt. IV, ch. 61, sec. 4301
Definitions
§ 4301. Definitions As used in this chapter— (1) “domestic air mail” means matter bearing postage at the rates of postage prescribed in sections 4303 and 4304 of this title which is mailed in the United States Postal Service for transportation by air and delivery by the United States Postal Service. (2) “air parcel post” means domestic air mail of any class weighing in excess of eight ounces.