What happened
Following a late arrival into Seattle, a flight crew prepared for a new departure. After the engines were shut down and the aircraft was chocked, a first officer conducted a preflight inspection. During this period, a ground baggage handler operating a tug was maneuvering around baggage carts near a belt loader. While attempting to drive away after loading carts, the handler's tug struck the side of the aircraft. The handler did not observe any damage during an initial glance and did not report the contact.
The subsequent flight proceeded normally during takeoff. However, while climbing through approximately 26,000 feet, the crew heard a loud bang, and the cabin depressurized. The crew donned oxygen masks and coordinated a descent to a lower altitude with Seattle Center. The aircraft completed an uneventful landing at Seattle-Tacoma International Airport in Seattle, Washington.
The investigation
A post-landing examination of the fuselage identified a hole measuring 12 by 6 inches located between the middle and forward cargo doors on the right side of the aircraft. Following the occurrence, the ground baggage handler admitted to having grazed the airplane with the tug while attempting to depart the area.