Shuttle Carrier Aircraft, with Discovery

The space shuttle has been around so long now that it's easy to forget one of its original claims to fame: it's a spacecraft that can also fly in the atmosphere like an airplane. That's only in its unpowered descent back to Earth, though.

The shuttle does require help getting off the ground. It rides a rocket when it's heading into outer space. And when it needs to make an aerial transit here in the earthly realm, it relies on the Shuttle Carrier Aircraft.

Actually, there are two of the shuttle-toting aircraft, both of them modified Boeing 747 jumbo jets that once served as commercial carriers. Here, in September 2009 following a mission to the International Space Station, one of the jets ferries the shuttle Discovery--which just yesterday lifted off on its final mission--from its landing strip at Edwards Air Force Base in California back to the Kennedy Space Center in Florida.