The Stratoliner was the first airplane to have a flight engineer as a member of the crew. The engineer was responsible for maintaining power settings, pressurization and other subsystems, leaving the pilot free to concentrate on other aspects of flying the aircraft. The Stratoliner was the first airplane with hydraulically boosted control surfaces (elevators and rudder) and the first airliner with geared two speed engine superchargers. Boeing built 10 Model 307s. In 1940, the 307s started flying routes to Latin America and from New York to Los Angeles, Calif. Production stopped at the onset of war, and five were drafted into the Army Transport Command as C-75 military transports.