14 CFR § 91.325

Unless provided for in this section, no person may operate a primary category aircraft carrying persons or property for compensation or hire in operations that:

Require an air carrier or commercial operator certificate issued under part 119 of this chapter;

Are listed in § 119.1(e) of this chapter;

Require management specifications for a fractional ownership program issued in accordance with subpart K of this part; or

Are conducted under part 129, 133, or 137 of this chapter.

Except as provided in § 91.326(c), no person may operate a primary category aircraft that is maintained by the pilot-owner under an approved special inspection and maintenance program except—

The pilot-owner; or

A designee of the pilot-owner, provided that the pilot-owner does not receive compensation for the use of the aircraft.

A primary category aircraft that is maintained by an appropriately rated mechanic or an authorized certificated repair station in accordance with the applicable provisions of part 43 of this chapter may be used to conduct flight training, checking, and testing for compensation or hire.