The passenger capacity of the aircraft was increased to 149 by extending the fuselage around the wing by meters (9 ft 5 in). The wing incorporated several changes for improved aerodynamics. The wingtip was extended 9 in (23 cm), and the wingspan by 1 ft 9 in (53 cm). The leading-edge slats and trailing-edge flaps were adjusted.  The tailfin was redesigned, the flight deck was improved with the optional EFIS (Electronic Flight Instrumentation System), and the passenger cabin incorporated improvements similar to those developed on the Boeing 757 .  The prototype -300, the 1,001st 737 built, first flew on 24 February 1984 with pilot Jim McRoberts.  It and two production aircraft flew a nine-month-long certification program.