Beechcraft 350 Super King Air airplane model. Design of an improved development of the successful King Air B200 began in August 1981, the 14 month design effort culminating in the first flight of the modernised 300 model in October the following year. Improvements to the B200 were many, with the main change being the installation of more powerful PT6A60A turboprops in place of the 42s of the earlier model. Other changes included reprofiled and more aerodynamically clean engine cowls and exhausts and extended wing leading edges, plus minor internal changes. Both empty and max takeoff weights were also increased.