The Learjet Model 35 and Model 36 are a series of American multi-role business jets and military transport aircraft manufactured by Learjet between 1973 and 1993. When used by the United States Air Force, they carry the designation C-21A. Learjet was acquired by Bombardier Aviation in 1990 as a subsidiary, so the aircraft is also known as the Bombardier Learjet 35.
When first released in 1973, the Learjet 35 was among the fastest medium haul jets of its era. As of 2020, more Learjet 35s have been sold than any other Learjet aircraft, with many still in service after 50 years.
The aircraft are powered by two Garrett TFE731-2 turbofan engines. Its cabin can be arranged for six to eight passengers. The longer-range Model 36 has a shortened passenger area to provide more space in the aft fuselage for fuel tanks.
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. 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.
By 2018, 1980s Learjet 35As start at $500,000.
When released in 1973, Learjet's marketing claimed that the Learjet 35 was among the fastest business jets in its class. 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.
Because of its speed and long range, leaders of many nations bought the aircraft as their primary or secondary jet. Countries who did this include: Brazil, Chile, Finland, Switzerland and Saudi Arabia among others.
During the Cold War, the Finnish Air Force used the Learjet 35/36 as a shorter range AEW&C aircraft, for monitoring Soviet bombers and fighter jets coming over the Baltic Sea and over the Arctic. Learjet 35s made the bulk of Argentina's Escuadrón Fénix flights during the 1982 Falklands War mainly on diversion and reconnaissance flights.
Production on the 35/36 series ceased in 1994. There are still well over 500 Learjet 35s in service around the world, despite the model being almost 50 years old.
As of January 2018, the U.S. National Transportation Safety Board database lists 25 fatal accidents for the 35/35A, and two for the 36/36A.
The original Model 35 was powered by two TFE731-2-2A engines and was 13 inches (330 mm) 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.
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 (3,520 L; 775 imp gal) 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, N10BD, owned by Cable Television Founder Bill Daniels and piloted by Mark E. Calkins, former astronaut Pete Conrad, Paul Thayer, and Daniel C. Miller completed an around-the-world flight in a record 49 hrs, 21 min, and 8 sec. The record remains standing as of 2015, and this aircraft is now on display in Terminal C of Denver International Airport.
The Model 36 is essentially identical to the 35, except that it has a larger fuselage fuel tank, giving it 500 miles (800 km) longer range, but reducing the passenger area's length by 18 inches (460 mm). It was certified, along with the 35, in July, 1974.
Like the 35A, the Model 36A has upgraded engines and a higher maximum gross weight. It was introduced in 1976, replacing the 36.
The C-21A is a United States military designation for an "off the shelf" variant of the Learjet 35A for the United States Air Force, with room for eight passengers and 42 ft3 (1.26 m3) of cargo. In addition to its normal role, the aircraft is capable of transporting litters during medical evacuations. Delivery of the C-21A fleet began in April 1984 and was completed in October 1985.
There are 38 Air Force active duty aircraft, and 18 Air National Guard aircraft in the C-21A fleet. On 1 April 1997, all continental U.S.-based C-21As were realigned under Air Mobility Command, with the 375th Airlift Wing at Scott Air Force Base, Illinois, as the lead command. C-21As stationed outside the continental United States are assigned to the theater commanders.