[Yo-Yo]

I understand the military advantage of launching an ICBM out of the back of a C-5. I can even see the advantage of being able to launch a spy payload into any orbit on short notice.

But what advantage would a manned missile have over a ground launch? You gain maybe 20,000 ft altitude, about 5 seconds of burn, and your airspeed is esentially zero.

Maybe the only advantage I see is the ability to reach the ISS without having to wait for a specific launch window by placing the aircraft at the appropriate location on the globe?

[ErnstStavroBlofeld]

You have rapid response and the ability to launch from virtually any location to any orbit and target.