The Beech King Air 100 is a stretched version of the King Air 90. Its longer cabin may seat six to seven passengers depending on configuration.

The typical cabin layout of the King Air 100 consists of a four-place club arrangement, a fifth individual seat, and a two-seat divan. An eighth space is available in the belted, enclosed lavatory. The aircraft also features five cabin windows on each side; an increase over the King Air 90’s three per side.

Like the Model 90, the King Air 100 has been upgraded through a series of several variants. The original Model 100 offered an increase in maximum take-off weight over the 90 from which it was designed, a reduced wingspan, twin-wheel main landing gear, larger elevator and rudder areas, and used two PT6A-28 engines. The next model was the military version A100, which had a further increase in maximum take-off weight, higher fuel capacity, and four-bladed propellers. The civilian version B100 incorporated the same improvements and was powered by Garrett AiResearch TPE-331 engines.