 North American designed a new streamlined plexiglass canopy for the P-51B which was later developed into the teardrop shaped bubble canopy.In late 1942, the tenth production P-51B-1-NA was removed from the assembly lines.From the windshield aft the fuselage was redesigned by cutting down the rear fuselage formers to the same height as those forward of the cockpit; the new shape faired in to the vertical tail unit.