RAF Mount Pleasant is the newest permanent airfield in the Royal Air Force. The RAF previously had a small airfield at Port Stanley Airport after the end of the hostilities in 1982. During the Falklands War when the islands were occupied by Argentine military forces, British aircraft were sent to disable the runway with RAF Strike Command Vulcan bombers (Operation Black Buck) and Royal Navy Sea Harriers. The first two Black Buck missions were flown under tactics to make it reasonably probable at least one of twenty-one 1,000-pound bombs dropped would hit the target. On the first mission one 1,000-pound (450 kg) bomb hit the edge of the runway. The damage was easily repaired by Argentine engineers. C-130 Hercules transport aircraft were able to bring in supplies and take out casualties until the end of the conflict using one side of the runway. Pucará, Fokkers and Aermacchi AM-339 fast-jet fighters also operated from the runway from the first until the last day of the campaign. The second Black Buck mission failed to hit the runway. Argentine aircraft were moved north to the mainland to defend Buenos Aires. At the end of hostilities, the runway was fully repaired by British military engineers. After the surrender of the Argentine ground forces on the islands, the British still faced the problem of potential Argentine air attacks from Argentina, so an aircraft carrier had to remain on station to guard the islands with its squadron of Sea Harriers until the local airfield was prepared for jet aircraft. HMS Hermes was the first to take guard duty, whilst HMS Invincible went north to change a main engine at sea. Invincible then returned to relieve Hermes which urgently needed to return to the UK for boiler cleaning. Invincible returned until she was relieved by the newly built HMS Illustrious, which was quickly rushed south and commissioned during the journey. Once the Port Stanley runway was available for jets, Illustrious was relieved by 23 Squadron operating the F-4 Phantom FGR.2. Initially stationed at RAF Stanley, the unit moved to Mount Pleasant upon its opening. In order to deter further Argentine aggression or invasion attempts, the British Government considered it necessary to enhance the military presence in the Falklands. However, the temporary military airfield at RAF Stanley was restricted by the length and strength of its runway. Therefore, in June 1983, the British Government announced that a new military airfield would be constructed at Mount Pleasant, the option being considered to be more cost effective and straightforward than upgrading RAF Stanley. It would also allow RAF Stanley to remain operational whilst the new airfield was constructed. The Ministry of Defence reached a voluntary agreement to purchase 8,300 acres (3,400 ha) of farmland for £55,000, with severance compensation assessed at £100,000. To allow existing agricultural operations to continue, Mount Pleasant House and other farm facilities were relocated at a cost of £83,877. The airfield at Mount Pleasant was constructed by Mowlem-Laing Amey Roadstone Construction, a consortium of British civil engineering and construction firms Mowlem, John Laing Group and Amey plc. At the construction stage the airfield was called the Falkland Island Strategic Airfield or FISA and was designed to accommodate military as well as civil wide-body aircraft, enabling efficiencies in the running costs and time taken to support the Falklands garrison. The construction and shipping of materials to the Falklands was expected to cost approximately £190 million. Additional costs included the provision of a road between Stanley and Mount Pleasant and the installation of communication and navigation aids, bringing the overall cost to approximately £215m. Construction began in Autumn 1983 and the new runway was expected to be available for use by April 1985, with the wider airfield complete by February 1986.