The Air Start unit used to start the 720 plugged into the l/h fuselage just fwd of the wing. This noisy beast was also very heavy. Towing it slowly was advisable as it took some stopping. On the flight deck one day the aircraft was jolted violently to the left. Rushing downstairs we discovered that an air start had disconnected from the tow vehicle when being positioned and embedded itself in the rear fuselage by the aft cargo hold. Morning departures for up to 6 720 normally parked next to each other within a few minutes of each other was always exciting. Lots of noise, movement and......oh the memories.