Can You Start An Airplane Engine Manually? Airplane engine manual start, also known as air starting, is a process where an engine needs a rush of air to make its compressor spin fast enough to start running by itself. This air can come from another running engine or the APU which is a small engine on the plane. To make this happen, a special valve is opened to let air flow into the engine being started. In some cases, like in the video, a person could be turning this valve by hand. Sometimes, th