Because of dense air at low altitudes, the B-58 could not fly at supersonic speeds and its moderate range was reduced further, negating the costly high-speed performance of the aircraft. Despite shortcomings, the type had its advocates within the service; according to Gunston and Gilchrist, when Secretary McNamara had requested proposals for a new manned Mach 2 bomber, General Thomas S. Power responded with a request for the B-58 to be put back into production. In late 1965, McNamara ordered retirement of the B-58 by 1970; the principal reason given for this directive was the high sustainment cost for the fleet. On 29 October 1969, the Department of Defense announced that the type would be withdrawn from service on 31 January 1970.