The RC-135W Rivet Joint, also known as Airseeker, is a surveillance aircraft used to absorb electronic emissions and intelligence from radar and other communication systems, hitting heights of up to 39,000 feet.
The RAF's 51 Squadron operates three Rivet Joint planes, part of the Royal Air Force's Intelligence Surveillance Target Acquisition and Reconnaissance Force, based at RAF Waddington.
Uniquely, they are supported by a joint arrangement between the US Air Force and the Ministry of Defence (Rivet Joint Co-operative Programme), worth £970m, according to the Royal Air Force.
Originally due to expire in 2025, the agreement has now been extended to 2035.
The co-operation includes maintenance, spare parts, engineering support, technical data and access to capability updates.
Powered by four 21,600lb st (96kN) CFM International F108-CF-201 turbofan engines, the aircraft is 135ft long and 42ft tall, with a 131ft wingspan.
It can fly up to 470 knots for around 3,900 miles up to 39,000ft, the RAF says.
The aircraft boasts a new state-of-the-art 'glass' flight deck, which the RAF says makes flying operations easier and safer for pilots, as well as digital flight instrument displays and large LCD screens, rather than traditional dials and gauges, following an upgrade.
The aircraft is based on Boeing's Model 367-80 'Dash 80' prototype, which was rejected by airlines, but welcomed into service with the US Air Force (USAF) where it influenced the design for 'stratotanker' aircraft which have served the USAF in mid-air refuelling and photographic reconnaissance roles through the decades.
The RAF took delivery of three formerly USAF KC-135R aircraft from November 2013, to replace its Nimrod fleet – retired in 2011 after 37 years in service.
Rivet Joint aircraft have been deployed on missions including Operation Shader – the operational code name used for the UK's contribution to the US-led mission against IS.
It joined the US Air Force, US Navy and Royal Netherlands Air Force to test NATO's co-ordination from every angle of the battlefield on a recent Baltic Sea exercise.