The first RC-135W Rivet Joint intelligence-gathering aircraft for the U.K. Royal Air Force (RAF) has been delivered to its main operating base at RAF Waddington.

The aircraft — ZZ664 — arrived at Waddington on Nov. 12 after a flight from Majors Field in Greenville, Texas, via Bangor, Maine. The aircraft, which was converted from a 1964-vintage KC-135R tanker, is the first of three RC-135s destined for the RAF under the Airseeker program, filling the capability gap in electronic and signals-intelligence gathering left open by the retirement of the Nimrod R1 in 2011.

The RAF is the first export customer for the Rivet Joint, and the $1 billion program is considered to be one of the most complex Foreign Military Sales purchases ever completed between the U.K. and the U.S.

ZZ664 was rolled out of L-3’s facilities in Greenville in early May and made its first post-conversion flight at the end of July. According to RAF officials, the aircraft achieved its flight trials ahead of schedule, allowing it to be delivered early.

The RAF is due to declare an initial operating capability with a single RC-135 in October 2014; new aircraft will then be delivered every two years, with full operating capability expected in mid-2017, six months earlier than initially planned.

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 delivered with the baseline 10.2 system, the same standard as recently updated Air Force aircraft. New baselines for the Rivet Joint are developed every two years. Aircraft enter an 18-month maintenance program every four years in which they receive the latest upgrade, allowing the aircraft to emerge two baselines higher than when they enter maintenance. At any one time, the combined U.S. and U.K. fleet contains aircraft of at least two different baseline standards and sometimes three. The second and third aircraft will feature baselines 11 and 12, respectively.

With a hand in the program, the British also should get a say in the development of future upgrades and baselines.

Once in operational service, the aircraft will be operated by the RAF’s No. 51 Sqn., which operated the Nimrod R1, an aircraft that for many years the RAF refused to disclose as being in operation because of the type’s intelligence-gathering capabilities. In preparation for the Rivet Joint’s arrival, 51 Sqn. crews flew missions with the Air Force’s 55th Reconnaissance Wing to gain experience on the type. U.K. crews already have achieved in excess of 32,000 flying hours and 1,800 sorties with the 55th Wing.