About the Lockheed C-5 Galaxy The Lockheed C-5 Galaxy is a military transport aircraft designed to provide strategic heavy airlift over intercontinental distances. It is the largest American military transport and one of the largest military aircraft in the world, designed to carry outsize and oversize cargo. The C-5 was developed and produced by Lockheed and is operated by the United States Air Force.  In 1961, several aircraft companies began studying heavy jet transport designs that would replace the C-133 transport and complement C-141 Starlifters.