They are fitted with missile defence and radar jamming systems as well as electronics designed to withstand the electromagnetic pulse of a nuclear blast.
As a security measure, Marine One often flies in a group of identical helicopters acting as decoys.
It is also usually accompanied by two or three Osprey MV-22s – tilt-rotor aircraft referred to as “green tops” that combine the vertical landing ability of a helicopter with the flying speed and efficiency of an aeroplane.
The Ospreys carry support staff, special forces and secret service agents, who are tasked with dealing with any mid-flight emergency.