The Tristar K1 and KC1 are strategic tanker conversions of the Lockheed L-1011-500 Tristar commercial airliner. The Tristar K1 can  be fitted with up to 204 passenger seats for the trooping role. 

The Tristar KC1 tanker/freight aircraft have a large 140 x 102 inch, cargo door and a roller conveyer system capable of accepting up to 20 cargo pallets or seating for up to 196 passengers. Linked pallets can be used to permit the carriage of vehicles. It can carry on 136 tonnes of fuel which, in the air-to-air refuelling (AAR)  role, is transferable through the 2 x centre- line Hose Drum Units (HDUs); however, only one HDU may be used at a time with a fuel transfer rate is in excess of 2,000kg/min.

Also in service is the Tristar C2. This aircraft can carry 265 passengers and 35,000 pounds of freight over ranges in excess of 4,000 miles.

The Tristar normally cruises at 525mph and with a payload of 50,000 pounds has a range in excess of 6,000 miles. The aircraft entered service in early 1986 with No 216 Sqn which reformed at RAF Brize Norton on 1 Nov 1984.

Recent operations in Afghanistan and Iraq have seen RAF Tristars heavily involved in refuelling operations. 

Photo Crown Copyright  DCC (RAF)