The plane could now carry 149 passengers, because the fuselage of the plane was made bigger. Many changes were made to the wings. The tip of the wing was made longer by . The wingspan was also made bigger. The flaps on the wings were changed. The flight deck (cockpit) was improved with electronic displays. However, airlines could choose not to have these in their planes. The main cabin (where the passengers sit) was also made better. It looked similar to the cabin of a Boeing 757. The prototype of the 737-300 first flew on 24 February 1984. Its pilot was Jim McRoberts.