The U.K. Royal Air Force and the U.S. Air Force are working on a memorandum of understanding (MOU) that will give the U.K. access to tankers equipped with refueling booms to support its fleet of RC-135 Rivet Joint intelligence-gathering aircraft.

Officers close to the Airseeker program, which will cover the procurement of three Boeing RC-135W Rivet Joints, tell Aviation Week they hope to have the MOU in place by the end of this year when the first RAF Rivet Joint arrives in the U.K. The support is essential as the U.K. does not have any air-to-air refueling aircraft fitted with a boom, and there are no plans to add a probe to refuel from drogue-equipped aircraft in a bid to reduce costs in the Foreign Military Sales program.

According to officials the endurance of the RC-135 will be limited from the 9,000-ft. runway of the aircraft’s planned homebase of RAF Waddington, Lincolnshire. Officials point out that the U.K. ISTAR (intelligence, surveillance, target acquisition and reconnaissance) assets are regular users of U.S. Air Force tankers based in Europe. British E-3D Sentry airborne early warning aircraft routinely top-up their tanks from U.S. Air Force KC-135s based at RAF Mildenhall in the U.K. or from aircraft detached to the NATO base at Geilenkirchen in Germany which support the E-3As flown by NATO’s E-3A Component.

During coalition operations, RAF aircraft regularly take fuel from U.S. tanker aircraft, and vice-versa, but questions remain about what happens if the Rivet Joints are required for use in a non-coalition operation that does not involve the U.S. — for example, an operation in the South Atlantic and the Falkland Islands.

The Rivet Joints will fill the capability gap that was left following the retirement of the Nimrod R1. The first of the RC-135s destined for the RAF was rolled out of L-3’s facilities in Greenville, Texas in early May. The U.K. is the first export customer for the aircraft.

Because the Boeing C-135 is no longer in production, the Rivet Joints are being converted from a trio of 1964-vintage Boeing KC-135 Stratotankers.

The RAF is due to declare an initial operating capability with a single RC-135 in October 2014, and the aircraft will then be delivered every two years, with full operating capability expected in December 2017.

Like U.S. Air Force Rivet Joints, the British aircraft will undergo updates every few years to receive the latest baseline of equipment. The first aircraft has been fitted with the baseline 10 system, while the second will feature baseline 11 and the third baseline 12. With a hand in the program, the British also should get a say in the development of future upgrades and baselines.