The missing aircraft was a Boeing 377 Stratocruiser, serial number 15960, registered N90944.
 It first flew on August 30, 1949, as Flagship Ireland for American Overseas Airlines, and was transferred to Pan American World Airways on September 28, 1950, after Pan Am's acquisition of American Overseas Airlines.
 At the time of the accident, the airframe had accumulated a total of 23,690 logged flying hours.
 The four engines of the aircraft had total times ranging from 13,459 hours to 16,961 hours, and had been overhauled within the last 1,249 hours of flight.
 Investigations by the CAB found that "the aircraft, engines, and propellers had been maintained as prescribed and were within their time limitations."

The accident was the second worst accident involving the Boeing Stratocruiser.
  The aircraft type had a long history of mechanical problems.
 Several of the aircraft had experienced runaway propellers, a situation where the pilots were unable to control the pitch of the propellers and centrifugal force causes the blades to adjust to the lowest pitch, leading to aerodynamic instability.
  In 1952, Pan Am Flight 202 crashed in the Amazon Basin after its engine and propeller failed in flight.
 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.

The aircraft had experienced two incidents shortly before its final flight.
 On June 18, 1957, it had suffered a runaway propeller as it departed San Francisco.
 The crew was unable to feather the propeller and it performed an emergency landing back at San Francisco.
  On September 19, 1957, during a flight between San Francisco and Honolulu, the crew heard a loud noise, described as "similar to dropping the navigation stool on the flight deck".
 In-flight inspections were performed and the plane landed without incident after the crew found no abnormalities.
 A company inspector later investigated and found nothing out of the ordinary, noting in his report "... you could duplicate loud noise by stepping hard on door between cockpit and cargo.
 Also loud bang could be duplicated by dropping forward toilet lid."

The aircraft that had been built immediately before the one on the missing flight, the Sovereign of the Skies, Pan Am Flight 6, serial number 15959, had encountered mechanical problems and had ditched in the Pacific Ocean on October 16, 1956, after two of its engines had failed.
 In that incident, all 31 passengers 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.
The missing aircraft was a Boeing 377 Stratocruiser, serial number 15960, registered N90944.  It first flew on August 30, 1949, as Flagship Ireland for American Overseas Airlines, and was transferred to Pan American World Airways on September 28, 1950, after Pan Am's acquisition of American Overseas Airlines.  At the time of the accident, the airframe had accumulated a total of 23,690 logged flying hours.  The four engines of the aircraft had total times ranging from 13,459 hours to 16,961 hours, and had been overhauled within the last 1,249 hours of flight.  Investigations by the CAB found that "the aircraft, engines, and propellers had been maintained as prescribed and were within their time limitations."
The accident was the second worst accident involving the Boeing Stratocruiser.   The aircraft type had a long history of mechanical problems.  Several of the aircraft had experienced runaway propellers, a situation where the pilots were unable to control the pitch of the propellers and centrifugal force causes the blades to adjust to the lowest pitch, leading to aerodynamic instability.   In 1952, Pan Am Flight 202 crashed in the Amazon Basin after its engine and propeller failed in flight.  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.
The aircraft had experienced two incidents shortly before its final flight.  On June 18, 1957, it had suffered a runaway propeller as it departed San Francisco.  The crew was unable to feather the propeller and it performed an emergency landing back at San Francisco.   On September 19, 1957, during a flight between San Francisco and Honolulu, the crew heard a loud noise, described as "similar to dropping the navigation stool on the flight deck".  In-flight inspections were performed and the plane landed without incident after the crew found no abnormalities.  A company inspector later investigated and found nothing out of the ordinary, noting in his report "... you could duplicate loud noise by stepping hard on door between cockpit and cargo.  Also loud bang could be duplicated by dropping forward toilet lid."
The aircraft that had been built immediately before the one on the missing flight, the Sovereign of the Skies, Pan Am Flight 6, serial number 15959, had encountered mechanical problems and had ditched in the Pacific Ocean on October 16, 1956, after two of its engines had failed.  In that incident, all 31 passengers 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.
Pan Am Flight 7