American manned spaceplane. Study 1968. In late 1968 the USAF Flight Dynamics Laboratory proposed its Integrated Launch and Re-entry Vehicle. This was a 1.5 stage-to-orbit concept with an external drop tank.
AKA: ILRV;Integrated Launch and Re-entry Vehicle. Status: Study 1968.
The Air Force continued studies on the design until NASA Phase A space shuttle contracts, and the shuttle that ultimately flew owed much to USAF ILRV concepts.