On November 8, 1957, the Boeing 377 Stratocruiser 10-29 serving the flight, named Clipper Romance of the Skies, crashed in the Pacific Ocean en route to Honolulu International Airport from San Francisco.

Despite theories that the plane may have been the victim of sabotage, poor maintenance, or in-flight fire, investigators could not find enough evidence to support any definite conclusion.

[1]: 15 At 5:04 p.m., the captain made a routine position report while the flight was 1,028 nautical miles (1,180 mi; 1,900 km) east of Hawaii.

[7] At 6:42 p.m., Pan Am notified the United States Coast Guard that it had not heard from the plane in more than 90 minutes, which was considered unusual, but not necessarily alarming.

[7] Pan Am dispatched a sister Stratocruiser from San Francisco, loaded with supplies that it could drop to the ocean surface if needed, and sent a Douglas DC-7 to the search area with enough fuel to stay airborne for 16 hours.

[11] Pan Am officials expressed confidence that the craft could stay afloat "almost indefinitely" if it had been forced to land in the ocean and its fuselage had not been punctured.

[14] Pan Am pilots who were personal friends of the lost crew listened to recordings of the radio transmissions and said it was unlikely that the messages had originated from the missing flight.

[15] A Pan Am pilot en route between San Francisco and Honolulu also reported seeing a yellow, cylindrical object about 2 by 4 feet (60 by 120 cm), with a dye marker nearby.

[1]: 2 [17] A total of 19 victims were pulled from the water; 14 of them were wearing life jackets, and none of them had shoes on, suggesting that the passengers had received some advance warning before the crash.

The Navy reported that all of the victims had external injuries and multiple fractures, and concluded that the plane had probably struck the water with tremendous force.

Investigations by the Civil Aeronautics Board (CAB) found that "the aircraft, engines, and propellers had been maintained as prescribed and were within their time limitations.

[15] In 1955, Pan Am Flight 845/26 ditched in the Pacific Ocean off the coast of Oregon with four fatalities after one of the aircraft's propellers failed and caused the engine to separate from the wing.

[25] All 31 people aboard on Flight 6 had been rescued, but the tail broke off on impact and the plane sank only 22 minutes after the forced landing, preventing a detailed investigation into the cause of the engine failures.

[1]: 14  Second officer William H. Fortenberry, acting as pilot-navigator on the flight, had worked for Pan Am since graduating from Spartanburg Community College in 1951.

[31] CAB investigators moved all of the recovered pieces of wreckage to a restricted area at the Pan Am overhaul station in San Francisco.

[1]: 2 [32] The 500 pounds (230 kg) of recovered material mainly consisted of the fuselage's secondary structure, interior trim and equipment, and numerous packages of mail.

[1]: 2  Investigators found no evidence of an in-flight fire, and laboratory tests of the charred pieces did not find any traces of prohibited or explosive material.

[19][34] CAB investigators conducted a study to determine how high concentrations of the gas could have occurred in the fuselage, and identified several possible causes.

[1]: 6  Investigators concluded that one probable source of the gas was an unexpected failure in one of the engines, such as one that released a propeller or turbocharger disk into the fuselage.

One scenario considered was the malicious introduction of pure carbon monoxide into the flight cabin; the gas would have been undetectable and could have incapacitated the crew, resulting in the crash.

[7] In 1949, Albert Guay had planted a bomb aboard Canadian Pacific Air Lines Flight 108 in a plot to kill his wife and collect the insurance money.

In 1955, Jack Gilbert Graham had planted a bomb in his mother's suitcase aboard United Airlines Flight 629 after purchasing a life insurance policy at the airport.

[7] CAB investigators dismissed the possibility of insurance-motivated sabotage, reporting that "no untoward amount" of life insurance had been taken out on any of the occupants of the plane.

[35] The passenger, a 41-year-old man from Scott Bar, California, named William Payne, had also purchased two air trip policies at the airport totaling $125,000.

[d] Payne's body was not one of the 19 recovered from the crash scene and the insurance company contended that there was no evidence that he was actually a passenger on the flight or that he had died.

At the time of the crash, Payne was heavily in debt; the company claimed that the reasons he gave for his trip to Honolulu did not justify the expense involved.

His widow, Harriet Payne, had also filed a $300,000[e] damage suit against Pan Am earlier that year, and denied the claim that her husband was not aboard Flight 7 when it went down.

[37] CAB investigators said that laboratory examination of the plane's wreckage had ruled out the possibility of a bomb explosion of any kind aboard the aircraft.