Some debate exists over the definition of space (see boundary to space), and hence that of spaceflight. The US defines spaceflight as over an altitude of 50 miles while the FAI defines it as over 100 km. For human spaceflights this is relevant for the X-15; as of 2003, 13 of these flights met the US criteria and among them 2 the FAI's.
For detailed listings, including dates and crew, see