The C-90 King Air prototype first flew on January 20, 1964. The civilian model of the King Air began in late 1964. The C-90 King Air has a pressurized cabin and has a maximum seating capacity of 10 people, including the pilot. On September 1970, the improved King Air was introduced and has an advanced pressurization and heating system for the cabin. There's a total of 507 C90s built.