Northrop said Friday the phase marks the start of a production interval in which a fuselage will be manufactured every day and a half.
Frank Carus, vice president and F-35 program manager at Northrop, said the company completed and delivered in May the 400th center fuselage to Lockheed and started in June the production of the 500th fuselage for the fighter jet.
Northrop produces the F-35 center fuselage on its integrated assembly line at its aircraft integration center of excellence in Palmdale, Calif.
The IAL facility uses predictive automation, robotics, virtual 3D and autonomous systems to support the center fuselage production.
Northrop also builds and maintains mission systems, avionics, sensor technology, maintainer and pilot training courseware, mission-planning software and low-observable platforms for the fighter jet in addition to the center fuselage and wing skins.