provision of ground infrastructure, training of personnel and ground supporting systems. In 2013, the UK government confirmed that crews from the RAF's 51 Squadron had been training and operating alongside their USAF colleagues since 2011, having achieved in excess of 32,000 flying hours and 1,800 sorties as part of the 55th Wing at Offutt AFB. The RAF received the first RC-135W in September 2013, which was deployed from July 2014 to support coalition action against combat Islamic State of Iraq and the Levant militants in Iraq. The second aircraft was delivered seven months ahead of schedule in September 2015, with over sixty improvements incorporated ranging from upgrades to the aircraft's mission systems to engine improvements providing increased fuel efficiency and durability. In due course, the first Airseeker will receive the same upgrades. The aircraft will be air-to-air refuelled in service by USAF tankers based in Europe, as the UK does not operate boom-equipped refueling aircraft and has no plans to adapt drogue-equipped aircraft. A U.S. Air Force RC-135W Rivet Joint reconnaissance aircraft was deployed numerous times to conduct reconnaissance missions around Poland and the Russian enclave of Kaliningrad during the 2022 Russian Invasion of Ukraine. Stated objectives include broadcasting a clear signal that the US, and thus NATO, is aware of Russian movements in the area of operations. Variants KC-135A Reconnaissance Platforms At least four KC-135A tankers were converted into makeshift reconnaissance platforms with no change of Mission Design Series (MDS) designation. KC-135As 55–3121, 55–3127, 59–1465, and 59-1514 were modified beginning in 1961. That year the Soviet Union announced its intention to detonate a 100 megaton thermonuclear device on Novaya Zemlya, the so-called Tsar Bomba. A testbed KC-135A (55–3127) was modified under the Big Safari program to the SPEED LIGHT BRAVO configuration in order to obtain intelligence information on the test. The success of the mission prompted conversion of additional aircraft for intelligence gathering duties. KC-135R Rivet Stand / Rivet Quick Not to be confused with the CFM F108-powered KC-135R tanker, the KC-135R MDS was applied in 1963 to the three KC-135A reconnaissance aircraft under the Rivet Stand program. The three aircraft were 55–3121, 59–1465, and 59–1514; a fourth, serial no. 58–0126, was converted in 1969 to replace 1465 which had crashed in 1967. Externally the aircraft had varied configurations throughout their careers, but generally they were distinguished by five "towel bar" antennas along the spine of the upper fuselage