Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. 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, 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. 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.