The hypersonic X-43A flew faster, but the X-51A flew longer. On May 26, 2010, the X-51A Waverider pushed itself to about Mach 5--the threshold of hypersonic travel--in a flight that lasted about 3 minutes, 20 seconds. (The X-43A hypersonic flights were on the order of about 10 seconds.) The Air Force had been hoping for 5 minutes and Mach 6, but it still considered the mission a rousing success. The most recent X-51A test took place in June, with more on the way.