The RAF had a mixed fleet of nine hose-and-drogue extended Lockheed L-1011 Tristar aircraft, which were operated by No 216 Squadron, based at RAF Brize Norton, Oxfordshire, in the air transport (AT) and air-to-air refuelling (AAR) roles. The aircraft, which previously saw airline service when they were owned by British Airways and Pan Am, were purchased by the RAF in the early 1980s. The six ex-British Airways aircraft were modified by Marshall of Cambridge (Engineering) into AAR tanker aircraft, with a twin, centreline hose-and-drogue configuration. Four aircraft were designated KC1, while two were designated K1. The installation included the addition of under-floor fuel tanks which increased the available fuel load by 43,900kgs. This allows a total fuel load of 139,700kgs to be carried, which can be used by the aircraft itself, or given away to receivers. Although the aircraft has two hosedrum refuelling units, only one can be used at a time, thus restricting AAR to single-point refuelling. On a typical AAR flight from the UK to Cyprus, or Gander (Canada), the KC1 can refuel up to four fast-jet aircraft and simultaneously carry up to 31 tonnes of passengers and/or freight. The addition of a large, fuselage freight-door and a roller-conveyor system allow outsized palletized cargo to be carried. Although the K1 model does not have the freight door, it retains a passenger- seat fit of 187 in the rear cabin, with baggage carried in the forward cabin. The three ex-Pan Am aircraft are largely unchanged from their airline days and operate in the passenger role, carrying up to 266 passengers. These aircraft are designated C2 and C2A and are used extensively for transporting troops to world-wide destinations in support of exercises and operations. All versions of the TriStar aircraft could operate in the aeromedical evacuation role, including the option of installing a full stretcher fit if required for the repatriation of casualties. All RAF Tristar's had a comprehensive avionics suite, which is undergoing modernization. As part of this program the aircraft were fitted with equipment which enabled them to operate as a JTIDS (Joint Tactical Information Distribution System) station and a radio relay station in areas of intensive military operations.