In 2006 Boeing started using a moving assembly line to build its market-leading 777 jetliner. The moving line is a leaner and more efficient manufacturing system. For now, the moving assembly line is used only during final assembly for the 777, moving it at a steady pace of 1.6 inches per minute during production. To make its 777 assembly line move, a tug is attached 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, items such as seats, overhead stow bins on the interior of the airplane are installed. In addition, functional testing is performed on various systems and the engines are attached. Boeing intends to complete a continuous, one-bay moving assembly line for the 777, which will include systems installation, final body join and final assembly for the airplane, sometime in 2008. This will be the most extensive moving production line used to build a commercial airplane.