Supersonic jet-powered cruise missile KSP v1.0.4
This cruise missile reaches a comfortable cruising speed of over 1337 m/s (almost mach 4) at a cruising altitude of ~ 20 km.
It has enough fuel to traverse half Kerbin's surface. More stats: https://host.tuxplace.nl/220200_2015-...
KerboScript used: https://host.tuxplace.nl/missile.ks