An order of 16 aircraft represents a brief glimpse at the future for the service - replacing the Reaper drone fleet.
A £65m contract to build the UK's first three Protectors expects the first to arrive in October.
The design is built on the existing Reaper drone system.
Protector can reach heights of 40,000 feet with a payload of up to 4,800lbs (2,177kg).
It can carry out missions in non-segregated civil airspace, enabling it to respond rapidly to requests across most of the globe.
The aircraft has a wingspan of 24m and can hit 210 KTAS (Knots True Airspeed).
General Atomics Aeronautical Systems was awarded the Ministry of Defence (MOD) contract to build the aircraft last July.
The company will also build three control stations and support equipment as part of the deal.
Due to enter service by mid-2024, the Protector RG Mk1, the British variant of the MQ-9B drone, will be capable of being flown anywhere in the world while being operated by personnel located at its Lincolnshire home base.
The UK's first Protector RG Mk1 aircraft completed its inaugural flight since coming off the production line last September, taking to the skies in the US for its first rounds of test flights.
The new aircraft are advanced, medium-altitude long-endurance RPAS which should enhance armed Intelligence, Surveillance, Targeting and Reconnaissance (ISTAR) capability.
It will also be the first RPAS to be designed, built and certified against stringent NATO and UK safety certification standards equivalent to manned aircraft, according to the RAF.
The drone, which has also been known as the MQ-9B SkyGuardian, will be fitted with the Brimstone missiles and Paveway bomb systems and will use onboard sensors to avoid other aircraft.
There are seven weapons stations on the drone, meaning a total of 21 Brimstone missiles could be carried.
This means a significant uplift over Reaper, which could carry four Hellfire missiles or two 500-pound laser-guided bombs.
Protector can fly consistently for up to 40 hours and will be deployed across the full spectrum of operations, including search and rescue, flood prevention or disaster response missions.
The fleet will also have advanced anti-icing and lightning protection, providing the RAF with the flexibility to operate in adverse weather conditions.
The UK and Belgium have agreed to look at ways they can work together and further enhance the new Protector drone programme, as both nations will be acquiring the MQ-9B aircraft.
Last year they signalled the growing desire for collaboration with a Bilateral Statement of Intent being signed by Chief of the Air Staff, Air Chief Marshal Sir Mike Wigston, and his Belgian counterpart.
Cover image: The UK's first Protector aircraft on the runway in the US during its maiden flight last year (Picture: RAF).