The pilots initially believed that a bomb had gone off inside the airliner, as this accident happened just two months after Pan Am Flight 103 was blown up over Lockerbie, Scotland. They began an emergency descent to reach an altitude where the air was breathable, while also performing a 180° left turn to fly back to Honolulu. The explosion damaged components of the on-board emergency oxygen supply system, as it was primarily located in the forward cargo sidewall area, just aft of the cargo door.
The debris ejected from the aircraft during the explosive decompression damaged the Number 3 and 4 engines. Engine 3 was experiencing heavy vibration, no N1 tachometer reading, and a low exhaust-gas temperature (EGT) and engine-pressure ratio, so the crew shut it down. At 02:20, an emergency was declared and the crew began dumping fuel to reduce the aircraft landing weight. The N1 reading of engine number 4 soon fell to almost zero, its EGT reading was high, and it was emitting flames, so they shut it down, as well. Some of the explosively ejected debris damaged the right wing's leading edge, dented the horizontal stabilizer on that side, and damaged the vertical stabilizer.