The Learjet 31 series of airplanes is essentially a Learjet 35 with a new wing longer by 4 feet and with almost 4-foot-high winglets instead of wingtip fuel tanks and large “delta fins” attached to the tail cone. These changes made the plane a much more docile one to fly, greatly improved field lengths and added 6 ktas to its normal cruise speed. Seats full range decreased to 1,225 nautical miles plus NBAA IFR fuel reserves. In 1988, the Learjet 31 won its Supplemental Type Certificate (STC). The 31ER got its STC in 1991.
