14 CFR § 91.407

No person may operate any aircraft that has undergone maintenance, preventive maintenance, rebuilding, or alteration unless—

It has been approved for return to service by a person authorized under § 43.7 of this chapter; and

The maintenance record entry required by § 43.9 or § 43.11, as applicable, of this chapter has been made.

No person may carry any person (other than crewmembers) in an aircraft that has been maintained, rebuilt, or altered in a manner that may have appreciably changed its flight characteristics or substantially affected its operation in flight until an appropriately rated pilot with at least a private pilot certificate flies the aircraft, makes an operational check of the maintenance performed or alteration made, and logs the flight in the aircraft records.

The aircraft does not have to be flown as required by paragraph (b) of this section if, prior to flight, ground tests, inspection, or both show conclusively that the maintenance, preventive maintenance, rebuilding, or alteration has not appreciably changed the flight characteristics or substantially affected the flight operation of the aircraft.