Often described as the workhorse of NASA's space shuttle fleet, because it logged the most flight hours of any shuttle, Discovery roared over the Air and Space Museum annex in Virginia this morning riding atop the back of a modified 747. (Take an Air and Space Museum quiz.)

(See pictures of the space shuttle soaring over D.C.)

Since the shuttles weren't designed to fly on their own, Discovery had to travel bolted to the 747 using the same attachments that once hooked the shuttle to its huge, orange external fuel tank for a launch.

Between now and Thursday, crews at the airport will "demate" the shuttle from its massive ride and prepare to roll the spaceship down the runway to