wing on the 1984 model Cessna 152. The "L" also introduced a longer dorsal strake that reached to the rear window. This was done more for styling than for aerodynamics and the empty weight accordingly went up over the "K". 879 were built in 1971. In 1972 the "L" received new fuel filler caps to reduce moisture seepage, and better seats and seat tracks. 1100 were built in 1972. The 1973 "L" model brought in lower seats to provide more headroom for taller pilots. 1460 of the 1973 models were built. The final "L" model was produced in 1974. The only change this model year was the propeller on the A150L Aerobat, to a new Clark Y airfoil that increased cruise by . 1080 150s were produced in 1974. Total "L" production was 4519, plus the 485 built by Reims as the F150L and 39 FA150L Aerobats. An additional 39 were built in Argentina by DINFIA as the A-150L. FRA150L Aerobat Reims produced a variant of the FA150L Aerobat with a Rolls-Royce Continental O-240-A engine, 141 built. The final Cessna 150 model was the 150M. It introduced the "Commuter II" upgrade package that included many optional avionics and trim items as standard. The "M" also brought an increased fin height, by . This increased the rudder and fin area by 15% to improve crosswind handling. The "M" was produced for three years: 1975–77. The United States Air Force Academy uses M variant (designated the T-51) for training and competition. Inertia-reel restraints became available as an option with the 1975 model year. 1269 1975 model 150Ms were built. In 1976 the "M" gained a suite of electrical circuit breakers to replace the previous fuses used. It was also fitted with a fully articulated pilot seat as standard equipment (this seat had been optional on some earlier models). 1399 were built. The 1977 model year was the last for the Cessna 150. It added only "pre-select" flaps, allowing the pilot to set the flaps to any position without the pilot having to hold the switch during flap travel, enabling the pilot to concentrate on other flying duties. Only 427 1977 model 150Ms were built as production shifted to the improved Cessna 152 in the early part of 1977. The many refinements incorporated into the 150 over the years had cost the aircraft a lot of useful load. The very first 150 weighed