14 CFR § 121.548
Aviation safety inspector's credentials: Admission to pilot's compartment
July 13, 2020
Whenever, in performing the duties of conducting an inspection, an inspector of the Federal Aviation Administration presents form FAA 110A, “Aviation Safety Inspector's Credential,” to the pilot in command of an aircraft operated by a certificate holder, the inspector must be given free and uninterrupted access to the pilot's compartment of that aircraft.
[Doc. No. 28154, 61 FR 2613, Jan. 26, 1996]