US investigators have determined that ground staff covered up an accident in which a vehicle damaged a McDonnell Douglas DC-9's fuselage, and allowed the jet to depart for a flight during which it depressurised.
The Northwest Airlines jet was being attended in daylight on the ramp at Syracuse, New York, by Air Wisconsin Airlines Corporation personnel ahead of operating a flight to Detroit on 18 May last year.
As the ground crew were dealing with baggage, the engine of their belt-loader stopped operating and a senior ground agent decided to use a luggage tug to push the loader away from the aircraft.
The tug drove within the safety-clearance zone - against regulations - and during the effort to push the loader away, the tug's cab contacted the fuselage.
In a probable-cause statement on the event, the National Transportation Safety Board says: "The senior ground agent then advised, 'Don't say anything' to one of the other ground agents who was working the flight with him."
The extraordinary decision to allow the DC-9 to depart led the jet to suffer cabin depressurisation as it climbed through 20,000ft. It performed an emergency descent to 10,000ft and diverted to Buffalo.
Inspection of the aircraft revealed a 12in-by-5in (30cm-by-13cm) tear in the right side of the fuselage, about 6ft (1.8m) ahead of the forward cargo door. There was also a crease in the skin ahead of the tear.
Marks on the tear were consistent with the damage having been caused by the tug. The jet, 38 years old at the time, had passed an airworthiness inspection the day before.
Two weeks after the accident the ramp-handling company reminded personnel of safety-zone regulations and underlined the importance of reporting immediately any damage to aircraft. It also issued additional training materials.
None of the 95 passengers and four crew members on board the DC-9 was injured during the depressurisation and diversion.