14 C.F.R. § 91.111 Operating near other aircraft.
Title 14 - Aeronautics and Space
(a) No person may operate an aircraft so close to another aircraft as to create a collision hazard. (b) No person may operate an aircraft in formation flight except by arrangement with the pilot in command of each aircraft in the formation. (c) No person may operate an aircraft, carrying passengers for hire, in formation flight.
Title 14: Aeronautics and Space
PART 91—GENERAL OPERATING AND FLIGHT RULES
Subpart B—Flight Rules
General
§ 91.111 Operating near other aircraft.