It has recently faced competition from light jet aircraft such as the Embraer Phenom 100, Honda HA-420 HondaJet and Cessna Citation Mustang; as well as from newer turboprop aircraft including the Piaggio P180 Avanti, and single-engine Piper Malibu Meridian, Pilatus PC-12, and Socata TBM.

In its original planned configuration, the Model 120 was to have been powered by two 917 shp (684 kW) Turbomeca Bastan VI engines.

[4] On May 15, 1963, Beechcraft began test flights of the proof-of-concept Model 87, a modified Queen Air with Pratt & Whitney Canada PT6A-6 engines.

On July 14, Beech announced a new type, and a month later began accepting orders for the "King Air", with deliveries to commence in Autumn 1964.

The F-models featured the T-tail of the Model 200 mated to the fuselage and wings of the E90, with PT6A-135 engines of 750 shp (560 kW) driving four-bladed propellers.

This engine change increased performance due to lower operating temperatures, improving both cruise speed and climb rate.

With a 275 kt (509 km/h, 316 mph) cruise speed, the C90GT was highly competitive with the new generation of Very Light Jets over short to medium distances, while providing a larger and more luxurious cabin.

[8] On May 21, 2007, during the 7th Annual European Business Aviation Convention & Exhibition in Geneva, Beechcraft announced the Model C90GTi updated version of the C90GT,[13] featuring the Rockwell Collins Proline 21 avionics package previously only offered for the B200 and B300 King Airs.

Textron, Beechcraft's parent company, stated that it intends to support the existing 90 series fleet indefinitely given the large number of aircraft being actively operated.

The next in the series was the B100, which featured 715 shp (533 kW) Garrett AiResearch TPE-331 engines as an alternative to the Pratt & Whitneys offered on other King Airs, and another increase in MTOW to 11,800 lb (5,350 kg).

The Japan Maritime Self-Defense Force (JMSDF) has operated a total of 40 C90 and C90A King Airs, with deliveries beginning in 1973.

These have been given various designations by the JMSDF and consist of 34 TC-90 trainers, five LC-90 transports, and a single UC-90 which is configured for photographic aerial survey.

[25] The U.S. military has used King Air 90s in various roles, primarily VIP and liaison transport, with designations including the VC-6A, the T-44 Pegasus, and the U-21 Ute.

[29] In 1993, the three surviving RU-21As that remained in military service were retired and sent to JW Duff Aircraft Salvage in Denver.

[31][32] The T-44A Pegasus is a trainer version, designated the Model H90 by Beechcraft, used to train United States Navy, Marine Corps, Coast Guard, and Air Force (USAF) pilots to fly multi-engine aircraft.

In August 2006, the Navy announced that after 29 years of operation, the T-44A fleet would be upgraded with modernized avionics systems, and redesignated T-44Cs.

During the administration of Lyndon Johnson, the USAF acquired a commercial off-the-shelf Model B90 King Air.

After Johnson left office, the aircraft continued to serve in the 89th Military Airlift Wing as a VIP transport until its retirement in 1985.

Among the numerous airframe modifications available: a cargo conversion for the 90 model, the CargoLiner, which replaces the rear door with a large pallet accessible cargo door, a heavy duty floor structure and cabin cargo liner, also a crew hatch for cockpit access for the crew in the 90, 100, and 200;[39] a Wing Front Spar Reinforcement Kit for both 90 and 100 Series aircraft,[36] a modification for the entire King Air line that entails reworking and extending the nose[40] to house a baggage compartment as well as the avionics normally found in the noses of King Air aircraft.