Aircraft Offences Act 1971

The person in command of an aircraft to which Part 2 or Part 3 of this Act applies may, on board the aircraft, with such assistance as is necessary, arrest without warrant a person whom he finds committing, or reasonably suspects of having committed, or of having attempted to commit, an offence referred to in that Part, and that person in command or a person authorised by him may hold the person so arrested in custody until he can be brought before a Justice of the Peace or other proper authority to be dealt with according to law.

The person in command of an aircraft to which Part 2 or Part 3 of this Act applies may, where he considers it necessary so to do in order to prevent an offence against that Part or to avoid danger to the safety of the aircraft or of persons on board the aircraft, with such assistance as he thinks necessary—

place a person who is on board the aircraft under restraint or in custody; and

if the aircraft is not in the course of a flight—remove a person from the aircraft.