Deliveries of the 90 King Air sample for civilian purposes, featuring a pressurized cockpit and 10 seats, began at the end of 1964. Two years later, this aircraft was supplanted by the King Air A90. The A90 was followed by the King Air B90, and then the King Air C90, with more advanced air conditioning and cab heating systems installed. Sample C90 was in serial production during 1982. He improved regularly. For example, the RT6A-21 engines were installed.