The Learjet 31 combined the fuselage, cabin and engines of the Model 35A/36A with the wing of the Model 55. Powered by two TFE731-2 turbofans, and incorporating winglets in place of tiptanks, plus 'Delta Fins' under the rear fuselage to give increased directional stability at all speeds, the Learjet 31 aerodynamic prototype first flew on 11 May 1987 and the type was certificated by the FAA in August 1988. Able to carry seven passengers and two crew over ranges up to 3076km, the LJ31 can cruise at 15545m. Two EFIS-equipped versions were ordered by Singapore Airlines specially configured for crew training and by mid-1991, when the type was superseded by the Model 31A and 31A/ER, about 30 had been delivered. The Learjet 31A replaced the earlier aircraft on the Wichita production line in July 1991 and features an integrated digital avionics package, and can also be equipped with a braking parachute installed internally under the tail. The extended-range Learjet 31A/ER is a Model 31A with a higher maximum takeoff weight and able to carry extra fuel.