In this photo provided by NASA, the space shuttle Discovery is suspended from a sling held by two cranes as the Boeing 747 is backed away at Washington Dulles International Airport on, April 19 in Sterling, Va.

The Space Shuttle Enterprise is towed from the Space hangar at the Smithsonian National Air and Space Museum Steven F. Udvar-Hazy Center in Chantilly on April 19 prior to a ceremony where Space Shuttle Discovery was officially received by the museum and placed on permanent display. Discovery is the first spaceship of the retired US shuttle fleet to enter its permanent home as a museum artifact, replacing the prototype Enterprise, which will be moved to a museum in New York.

The Enterprise, left, and Discovery, right, space shuttles face each other during the Discovery transfer ceremony, as the President's Own Marine Band performs the United States national anthem, at Smithsonian National Air and Space Museum's Steven F. Udvar-Hazy Center, in Chantilly, Va. on April 19. Discovery is the longest-serving orbiter in the space shuttle fleet.

The Enterprise space shuttle, left, and Discovery space shuttle, right, face each other during the Discovery transfer ceremony at Smithsonian National Air and Space Museum's Steven F. Udvar-Hazy Center in Chantilly, Va. on April 19.

Former U.S. Senator and astronaut John Glenn, seated, is applauded by former shuttle Discovery commanders at the National Air and Space Museum's Steven F. Udvar-Hazy Center at a ceremony for the arrival of space shuttle Discovery (background) in Chantilly, Va. on April 19.

Ashley Koen, left, and Stephanie Harris, right, wear Discovery space shuttle hats while standing in front of the Enterprise space shuttle before a ceremony at Smithsonian National Air and Space Museum's Steven F. Udvar-Hazy Center in Chantilly, Va. on April 19.

People gather at the base of the Washington Monument to watch as the U.S. space shuttle Discovery, on the back of a NASA 747 transport jet, flies over the National Mall on its way to its permanent display at the Smithsonian Institution, in Washington, April 17.

The space shuttle Discovery, riding atop a NASA 747 transport jet, does a final fly-by over the White House as tourists an Washingtonians watch and take pictures in Washington, April 17. Discovery will go on display at the National Air and Space Museum's Udvar-Hazy Center.

Space Shuttle Discovery, mounted atop a 747 shuttle carrier aircraft, flies over the U.S. Capitol during a flyover of the nation's capital on its final trip to its retirement place April 17, in Washington, DC. The longest-serving orbiter in the space shuttle fleet was flown from Kennedy Space Center in Florida to the Washington, DC area to be transferred to the Smithsonian National Air and Space Museum and will be placed on display in the museum's Steven F. Udvar-Hazy Center.

The Discovery space shuttle, mated with a Boeing 747 carrier aircraft, flies over the Washington Dulles International Airport in Chantilly, Virginia, USA, 17 April 17. NASA and Smithsonian officials will officially transfer Discovery to the Steven F. Udvar-Hazy Center during a ceremony 19 April 2012. Discovery is the longest-serving orbiter in the space shuttle fleet.

The NASA space shuttle Discovery is seen from the White House's North Lawn as it is flown over Washington, DC April 17. The space shuttle was carried by a modified 747 aircraft from Kennedy Space Center to Smithsonian National Air and Space Museum's Steven F. Udvar-Hazy Center in Virginia where it will spend its retirement after 39 missions.

People stand on the roof of the US Labor Department as US space shuttle Discovery sitting atop NASA's 747 shuttle carrier aircraft flies by in Washington,DC on April 17, as it arrives from Kennedy Space Center in Florida to be displayed at the National Air and Space museum near the US capital.

The space shuttle Discovery, attached to a modified NASA 747 aircraft, takes off headed for its final home at The Smithsonian National Air and Space Museum's Steven F. Udvar-Hazy Center in Chantilly, Virginia, from the Kennedy Space Center in Cape Canaveral, Florida April 17.

Photographers look on as space shuttle Discovery (above) is approached by a NASA 747 aircraft being towed into the Mate Demate facility at Kennedy Space Center in Cape Canaveral, Florida April 15, 2012. Discovery was later mated with the aircraft and is expected to be flown to its final home at The Smithsonian National Air and Space Museum Steven F. Udvar-Hazy Center in Chantilly, Virginia on April 17.

Backdropped by Earth's horizon and the blackness of space, space shuttle Discovery and its remote manipulator system/orbiter boom sensor system (RMS/OBSS) is featured in this image photographed by an STS-133 crew member while docked with the International Space Station.

The International Space Station is featured in this image photographed by an STS-133 crew member on space shuttle Discovery after the station and shuttle began their post-undocking relative separation. Undocking of the two spacecraft occurred at 7 a.m. (EST) on March 7, 2011. Discovery spent eight days, 16 hours, and 46 minutes attached to the orbiting laboratory.

The space shuttle Discovery is seen from the International Space Station as the two orbital spacecraft accomplish their relative separation on March 7 after an aggregate of 12 astronauts and cosmonauts worked together for over a week. The area below is the southwestern coast of Morocco in the northern Atlantic. During a post undocking fly-around, the crew members aboard the two spacecraft collected a series of photos of each other's vehicle.