The Beechcraft King Air series has its roots in the Twin Bonanza of 1951. That aircraft model was enlarged and re-engined to become the Model 65 Queen Air. The Queen Air design changed to incorporate a swept tail and pressurization. With the addition of Pratt & Whitney turboprop engines, the Queen Air became the Model 90 King Air.
The Model 90s have seen their way through the alphabet with the 90, A90, B90, C90, D90 (not built), E90, F90 and H90 (also not built). The Model 90 was first certificated in 1959. The F-90 is a C90 with more powerful Pratt & Whitney PT6A-135 engines, a T-tail, B200 wings, and a higher gross weight. The F-90/F90-1 was produced from 1979 to 1987.
The F90 series is the performance champion of the 90 series. It has more powerful engines than any of the other King Air 90 models. The King Air 90s seat five and have aft-lavatories, a nice feature in a small turboprop. The cabin is not round and is shaped more like a loaf of bread, which gives passengers more shoulder room.