Hold at FL210, MSA on all sectors above 12,000 feet and rwy elevation at 7000 feet fuel exhaustion would have confronted the crew with the attendant problems of loss of pressurisation. Could the the earlier speculative posts of confusion with the VOR for the rwy relate to onset of hypoxia, depending of course on exactly when the engines flamed out. Looking at the timing given by the ATC recording, it is conceivable they may have remained above 18,000 feet for the greater part of the final six minutes.