What happened
On June 21, Pan American Airways Flight 151 departed from Accra, Gold Coast, following a scheduled stop in Léopoldville. The aircraft, a Boeing 707, was operating an instrument flight plan toward Roberts Field, Monroviat, at an altitude of 16,500 feet. The flight carried a crew of nine and 31 passengers, with a total departure weight of 89,255 pounds.
During the flight, the aircraft maintained routine communication via high frequency radio-telephone with ground stations in Accra and Roberts Field. After passing over Cape Palmas, Liberia, at 0156, the crew requested permission to descend. The tower at Roberts Field cleared the aircraft to descend to 3,000 feet and provided local weather updates, including visibility and wind conditions.
At approximately 0305, the crew reported that radio interference from the Dakar beacon was affecting their ability to communicate with the Roberts Field station. While the tower attempted to coordinate turning off the Dakar beacon, the aircraft's communications became increasingly inconsistent. The final transmission from the flight occurred at 0315, when the crew contacted the tower on the VHF frequency but failed to acknowledge subsequent weather updates.
Following the loss of contact, search efforts located the wreckage near the village of Sanoyie, approximately 91 km northeast of Roberts Field. The impact and subsequent fire resulted in 40 fatalities.
Findings
Investigation into the accident revealed that the pilot initiated a descent below the required en route minimum altitude without first confirming the aircraft's exact position relative to the Roberts Field range station.