text: Guinness World Records Recognizes NASA X-43A Speed Record NASA -- Guinness World Records has recognized the world speed record set by NASA's hypersonic X-43A aircraft earlier this year in an experimental flight over the Pacific Ocean.     Using a scramjet engine, the unpiloted, 12 foot-long aircraft achieved Mach 6.83 -- almost seven times the speed of sound - - or nearly 5,000 mph, in a March 27 flight...