The airport tractor is a trailer that specializes in pushing airplanes.
When the aircraft needs to be launched from the bridge or the parking space to start the engine, the trailer is required to push the aircraft to the starting position. At this time, the aircraft has no power, and the rearward direction of the aircraft is completely controlled by the trailer.
The trailer is about 8 tons smaller and 16 tons larger. If the weight is too light, it will not move.