Along with the struts that attach a shuttle to the 747, another key modification to the jumbo jet is the addition of a pair of rectangular vertical stabilizers to the tail wings (aka horizontal stabilizers). At the aft end of the shuttle, meanwhile, the rocket exhausts are hidden by a streamlined cover meant to reduce turbulence. Seen here from above is the shuttle Columbia in March 2001.
The space shuttles measure 57 feet tall and 122 feet long, with a wingspan of 78 feet. The Shuttle Carrier Aircraft, by contrast, is 63 feet tall and 232 feet long, with a wingspan of 196 feet.
The typical cruising speed for the Shuttle Carrier Aircraft is about 250 knots, according to NASA, and the typical cruising altitude with the spacecraft attached is about 13,000 to 15,000 feet, with a range of roughly 1,000 nautical miles.