The captain's initial erroneous assumption that Maputo had suffered an electrical blackout was never reconsidered by the crew, despite evidence to the contrary. Throughout the descent the crew were in radio contact with the Maputo controller, who therefore had electrical power, and backup power generators were standard equipment for airport navigational aids. All the navigation aids at Maputo were determined by the board to be working at the time of the accident, although the aircraft was flying too far away and too low to receive the ILS and NDB signals. When announcing the distance remaining to Maputo the navigator was apparently referring to the Doppler navigation system, which was not accurate, rather than the DME equipment available on board which correctly displayed the distance to the Maputo DME beacon.