Known by its factory designation, line unit 1369, a 737-700 model was part of an educational effort at Southwest Airlines in 2003 to show its employees how an airplane is built. Southwest Airlines, an exclusive operator of 737 airplanes, posted the images and accompanying descriptive text on its company intranet. The documentation, included photos of the airplane’s nacelles and struts, as the airframe progressed through final assembly at Boeing's Renton factory.