NASA flew a third version of the X-43A on November 16, 2004. The modified Pegasus rocket was launched from a B-52 mother ship at an altitude of 13,000 m (43,000 ft). The X-43A set a new speed record of Mach 9.64 (10,240.84 km/h; 6,363.36 mph)[note 1] at about 33,500 m (110,000 ft) altitude,[10] and further tested the ability of the vehicle to withstand the heat loads involved.[11]