The Learjet Model 35 and Model 36 are a series of American multi-role business jets and military transport aircraft. When used by the United States Air Force they carry the designation C-21A.

The aircraft are powered by two Garrett TFE731-2 turbofan engines. Its cabin can be arranged for 6-8 passengers. The Model 36 has a shortened passenger area in the fuselage, in order to provide more space in the aft fuselage for fuel tanks. It is designed for longer-range mission capability.

The engines are mounted in nacelles on the sides of the aft fuselage. The wings are equipped with single-slotted flaps. The wingtip fuel tanks distinguish the design from other aircraft having similar functions.

The concept which became the LJ35 began as the Learjet 25BGF (with GF referring to "Garrett Fan"), a Learjet 25 with a then-new TFE731 turbofan engine mounted on the left side in place of the 25's General Electric CJ610 turbojet engine. This testbed aircraft first flew in May, 1971.^[1] As a result of the increased power and reduced noise of the new engine, Learjet further improved the design, and instead of being simply a variant of the 25, it became its own model, the 35.

In 1976 American professional golfer Arnold Palmer used a Learjet 36 to establish a new round-the-world class record of 22,894 miles (36990 km) completed in 57 hours 25 minutes 42 seconds.

Production on the 35/36 series ceased in 1994.

Learjet 35

The original Model 35 was powered by two TFE731-2-2A engines and was 13 inches longer than its predecessor, the Model 25. First flight of the prototype Model 35 was on 22 August 1973, and the aircraft was FAA certified in July, 1974. It could carry up to eight passengers. There were 64 base-model 35s built.

Learjet 35A

The Model 35A is an upgraded Model 35 with TFE731-2-2B engines and a range of 2,789 miles, with a fuel capacity of 931 US gallons (3,524 L) with refueling accomplished at ground level through each wingtip tank. It was introduced in 1976, replacing the 35. Over 600 35As were built, with a production line that ended with serial number 677, in 1993.

On February 12, 1996, a Learjet 35A piloted by Mark E. Calkins, Charles Conrad, Jr., Paul Thayer, and Daniel Miller completed an around-the-world flight in record time.  The record remains standing as of 2011.  This aircraft is now on display in Terminal C of Denver International Airport.