The UK has ordered 16 Protector aircraft from General Atomics-Aeronautical Systems Inc (GA-ASI), all of which will be based at RAF Waddington, the RAF's ISTAR (Intelligence, Surveillance, Target Acquisition and Reconnaissance) hub, in Lincolnshire.
Speaking at RAF Waddington, Defence Secretary Ben Wallace praised the flight of the SkyGuardian (which will be known as Protector when it enters RAF service) as a "huge milestone".
Protector can reach heights of 40,000 feet with a payload of up to 4,800lbs (2,177kg).
It has a wingspan of 24m and can hit 210 KTAS (Knots True Airspeed).
Cover image: The pre-production example of the UK's Protector aircraft (Picture: MOD).