Pegasus

Pegasus is a launcher that differs from its competitors. It is not fired from the ground, but is carried up to an altitude of 12 km under the fuselage of a Stargazer, a suitably modified Lockheed L-1011 commercial airliner, from which it is released. After a 5-second free fall, the rocket's engine is fired and it begins its ascension until it releases its payload into orbit.