Mo. Rev. Stat. § 305.140: Airman certificate to be kept in personal possession.

The airman certificate and certificate of airworthiness required by sections 305.120 to 305.160 shall be kept in the personal possession of the licensee when operating aircraft within this state, and must be presented for inspection upon the demand of any passenger, or any peace officer, or any official, manager or person in charge of any airport, or landing field in this state upon which he shall land.