on what would become the Tornado IDS (interdictor/strike) in 1968, the possibility of a variant dedicated to air defence had been quietly considered. While several American aircraft had been evaluated for meeting this requirement, they were all determined to be unsuitable. Despite Britain's strong interest in the air defense concept, it proved to be unattractive to the other European partners on the Tornado project, leading to its development being pursued solely by the United Kingdom. On 4 March 1976, the development of the Tornado ADV was approved and it was announced that 165 of the 385 Tornados that were on order for the RAF would be of the air defence variant. In 1976, the British Aircraft Corporation was contracted to provide three prototype aircraft. On 9 August 1979, the first prototype was rolled out at Warton; it performed its maiden flight on 27 October 1979, piloted by David Eagles. The second and third development aircraft made their first flights on 18 July and 18 November 1980 respectively. The third prototype was primarily used in the testing of the new Marconi/Ferranti AI.24 Foxhunter airborne interception radar. During flight testing, the Tornado ADV demonstrated its noticeably superior supersonic acceleration to the Tornado IDS, even while carrying a full weapons loadout. The test programme was greatly aided by the use of real-time telemetry, which broadcast live data from in-flight aircraft back to technicians on the ground. The Tornado ADV's differences compared to the Tornado IDS include a greater sweep angle on the wing gloves, and the deletion of their Krueger flap, deletion of the port cannon, a longer radome for the Foxhunter radar, slightly longer airbrakes, and the fuselage being lengthened to 1.36 m; the latter change permitted the carriage of four Skyflash semi-active radar homing missiles. This stretch was achieved by altering the Tornado's forward fuselage, which was built in the UK, via the addition of a plug immediately behind the cockpit, which had the unexpected benefit of reducing drag and making space for an additional fuel tank (Tank '0') carrying of fuel. The artificial feel of the flight controls was lighter on the Tornado ADV than on the IDS. Various other differences were present amongst the aircraft's avionics, displays, guidance systems and software packages. The Tornado F2 was the initial version of the Tornado ADV in RAF service, a total of 18 aircraft were built. Making its first flight on 5