A lengthened fuselage version of the 737-200, the 737-300, was ordered into production in March 1981, with first factory rollout January 17, 1984 (pictured here). First flight of the advanced derivative was on February 24, 1984, and the first delivery to US Air came on November 28, 1984. However, the joint leadoff customer Southwest Airlines placed the first 737-300 into passenger service on December 7, 1984. Design changes resulted in lower operating costs and a reduction in fuel burn up to 30% less than the 737-200.