What happened
On September 7, 2009, at approximately 2100 EDT, a Boeing 767-432ER, registration N840MH, was two hours into a flight from John F. Kennedy International Airport (JFK) to Venice Marco Polo Airport (VCE). During the flight, the cabin lights flickered, the Passenger Address System became intermittent and then failed, and the left-side oxygen masks deployed. The crew also noted a sulfur smell, though no smoke was visible. The flight diverted to Atlanta (ATL), where it landed without incident. There were 206 passengers, 8 cabin crew, and 3 flight crew on board, and there were no injuries.
The investigation
Maintenance crews inspected the area above the forward left-side lavatory and discovered a wire bundle containing numerous fractured and melted wires, along with soot on the bundle and the surrounding area. Evidence of chafing was found on a piece of support structure near the cable routing.
An examination of the wires within the bundle confirmed it included components for the lavatory power, the passenger address system, and the oxygen system. A review of Boeing installation drawings showed that the damaged wire bundle had been routed incorrectly and was not properly secured. While the investigation could not determine if the error occurred during manufacturing, maintenance, or a modification, a subsequent fleet inspection by the operator identified one other aircraft with the same incorrect routing, though no damage was found on that aircraft.