ZING!
From: https://www.absoluteastronomy.com/topics/Sh...arrier_Aircraft
Flying with the additional drag and weight of the Orbiter imposes fuel and altitude penalties. The range is reduced to 1,000 nautical miles (1,850 km), compared to an unladen range of 5500 nautical miles (10,100 km), requiring an SCA to stop several times to refuel on a transcontinental flight. The SCA has an altitude ceiling of 15,000 feet and a maximum cruise speed of Mach 0.6 with the orbiter attached. It takes a crew of about 170 a week to prepare the shuttle and SCA for flight.