On Nov. 8, 2006 The Boeing Company began using a moving assembly line for the first time to build its market-leading 777 jetliner. To make its 777 assembly line move during final assembly, Boeing uses a tug that attaches around the front landing gear of the airplane and pulls it forward. The tug has an optical sensor that follows a white line along the floor. During final assembly, mechanics install items such as seats, overhead stow bins and other items on the interior of the airplane. In addition, functional testing is performed on the various systems in the airplane and the engines are attached.