Beechjet 400Beechjet 400 airplane model. The Raytheon Beechjet traces its origins back to the Mitsubishi Diamond 2 bizjet, which Beechcraft acquired the design and production rights to in the mid 1980s. Beech reengined the Diamond 2 with P&WC JT15D5 turbofans, developed a new interior, and incorporated a number of other minor refinements. Deliveries of the Beechjet began in June 1986, with low rate production continuing until that model was replaced by the Model