with rear view window. T310Q Version of 310Q with turbocharged Continental TSIO-520-B or TSIO-520-BB engines and maximum takeoff weight increased to ; combined total of 871 310Q and T310Q built. Last production model, introduced in the 1975 model year, with Continental IO-520-M or IO-520-MB engines; three-blade propellers as standard; lengthened nose containing a baggage compartment; and maximum takeoff weight. T310R Version of 310R with turbocharged Continental TSIO-520-B or TSIO-520-BB engines; combined total of 1,332 310R and T310R built. 310S Original designation for the Cessna 320. 320 Skyknight Enlarged version of the 310F with six seats, larger cabin and two turbocharged engines; 110 built. 320A Skyknight First model with canted fuel tanks and minor changes; 47 built. 320B Skyknight First model with nacelle baggage lockers, minor changes; 62 built. 320C Skyknight Model with a longer cabin, optional seventh seat and minor changes; 73 built. 320D Executive Skyknight Model with reshaped rear windows and TSIO-520-B engines; 130 built. 320E Executive Skyknight Model with pointed nose, single piece windshield, modified landing gear, increased takeoff weight and minor changes; 110 built. 320F Executive Skyknight Model with minor changes compared to 320E; 45 built. L-27A United States military designation for the 310A, later changed to U-3A. L-27B United States military designation for the 310E/310M, later changed to U-3B. U-3A L-27A redesignated in 1963. U-3B L-27B redesignated in 1963. Colemill Executive 600 Conversion of models 310F to 310Q, replacing the engines with Lycoming TIO-540-J2BDs driving four-bladed propellers. Riley 65 Conversion offered for models 310 to 310G, replacing the engines with two 240-260 hp (179–194 kW) Continental O-470Ds or -470Ms. Riley Super 310 Conversion of Cessna 310/320 by fitting two 310 hp (231 kW) Continental TSIO-520J or 520N engines. Riley Turbostream Conversion of Cessna 310 by fitting two 350 hp Lycoming engines. Riley Rocket Conversion of Cessna 310 by fitting two 290 hp (216 kW) Lycoming IO-540-A1A5 engines and more fuel capacity. Riley Turbo-Rocket Riley Rocket with each engine fitted with two Riley-manufactured turbochargers. Cruise speed increased from to . Operators Civil The aircraft is popular with air charter companies and small feeder airlines, and is operated by private individuals and companies. Military operators Countries known to have operated the U-3/310 include. Argentina Argentine Air Force — Cessna 310 and 320 models Bolivia Colombia Colombian Air Force Republic of the Congo France French Air Force — 12 operated Haiti Haiti Air Corps Indonesia Indonesian Air Force Indonesian