These chronological lists include all crewed spaceflights that reached an altitude of at least 100 km (the FAI definition of spaceflight), or were launched with that intention but failed. The USA has adopted a slightly different definition of spaceflight, requiring an altitude of only 50 miles (80km). During the 1960s, 13 flights of the US X-15 rocket plane met the US criteria but only two met the FAI's. These lists include only the latter two flights; see the X-15 article for a list of all 13. As of 7 March 2009, there have been 268 manned spaceflights that reached 100 km or more in altitude, include 7 sub-orbital spaceflights.