Air-launch-to-orbit

Air-launch-to-orbit (ALTO) is the method of launching smaller rockets at altitude from a heavier conventional horizontal-takeoff aircraft, to carry satellites to low Earth orbit. It is a follow-on development of air launches of experimental aircraft that began in the late 1940s. This method, when employed for payload orbital insertion, presents significant advantages over conventional vertical rocket launches, particularly because of the reduced mass, thrust, cost of the rocket, geographical factors, and natural disasters.

Air launching has also been developed for sub-orbital spaceflight. In 2004 the Ansari X Prize $10 Million purse was won by a team led by Burt Rutan's Scaled Composites, launching the SpaceShipOne from the purpose-built White Knight carrier aircraft.

The first air-launch-to-space (not to orbit) occurred on 18 July 1958, with a test launch of the Bold Orion air-launched ICBM from a B-47 Stratojet carrier mothership. The first air-launch-to-orbit took place on 5 April 1990, with a Northrop Grumman Pegasus rocket carried by a NASA B-52.