14 C.F.R. § 135.73 Inspections and tests.
Title 14 - Aeronautics and Space
Each certificate holder and each person employed by the certificate holder shall allow the Administrator, at any time or place, to make inspections or tests (including en route inspections) to determine the holder's compliance with the Federal Aviation Act of 1958, applicable regulations, and the certificate holder's operating certificate, and operations specifications.
Title 14: Aeronautics and Space
PART 135—OPERATING REQUIREMENTS: COMMUTER AND ON DEMAND OPERATIONS AND RULES GOVERNING PERSONS ON BOARD SUCH AIRCRAFT
Subpart B—Flight Operations
§ 135.73 Inspections and tests.