This is not your ordinary airplane hangar.

Federal Express's first carrier will be parked near the Lockheed SR-71 Blackbird -- the fastest, highest-flying jet ever built. The Curtiss JN-4D Jenny, the aeronautical equivalent of the Ford Model T used during World War I, will be alongside the Space Shuttle Orbiter Enterprise, used for approach and landing tests in Earth's atmosphere in the late 1970s.

The Smithsonian Institution's annex to the National Air and Space Museum, under construction at Dulles International Airport, will showcase some of aviation's most famous and cool-looking aircraft.

The Steven F. Udvar-Hazy Center, scheduled to open in December 2003, is being built to show off the majority of the aircraft collection that the National Air and Space Museum on the Mall does not have room to hold.

Last week, museum administrators gave journalists a tour of the new Udvar-Hazy Center, the most recent in a series of media tours meant to heighten the public's anticipation as the opening nears.

The project, about 75 percent complete since construction began in April 2001, consists of the hangar, an attached IMAX theater and a 164-foot observation tower from which visitors can view airplanes taking off at Dulles and hear exchanges between air traffic controllers and pilots.

The 176-acre site will also include a restoration hangar, storage facility, archives unit and conservation lab.

The hangar, though, is the main attraction. Ascending walkways along interior walls of the cavernous building allow visitors to rise for closer views of old warplanes suspended in the air from arched steel trusses.

Visitors at the overlook of the hangar's main entrance can peer down at the floor on which all of the museum's heavy equipment will be exhibited. Included are an F-86 fighter jet used during the Korean War and the Lockheed SR-71 Blackbird, a sleek machine designed in the early 1960s that traveled coast to coast in 68 minutes at more than three times the speed of sound and is still the world's fastest.

Another prized possession is the B-29 named Enola Gay, which is currently in 52 pieces in the Smithsonian's storage facility in Maryland. It dropped the atomic bomb on Hiroshima during World War II.

The exhibits are so captivating that they are not only for airplane aficionados, said John R. Dailey, director of the museum and a retired Marine Corps general.

"The millions of people who come every year to our museum downtown are not all airplane nuts," Dailey said. "These planes will be inspiring to everyone."

Officials have raised about $220 million of the museum's $311 million price tag from private donors, the largest being Udvar-Hazy, a jet-leasing magnate who contributed $66 million.

The Dulles annex will hold 70 planes when it opens in December 2003 to mark the centennial of the Wright brothers' first powered flight. By 2007, the hangar will boast more than 200 planes.

Museum officials also say they have reached agreement with Air France to obtain a Concorde jet, the supersonic transport that speeds the wealthy set across the Atlantic Ocean, when the airline decides to retire one.

Because installing 200 planes will take four years, visitors will be able to see many of them placed in mid-air from the steel trusses.

In the meantime, craftsmen who have massive paint and concrete jobs ahead of them are working fast so museum officials can start stocking the hangar in March with planes.

The Smithsonian considered various airfield sites nationwide, including Baltimore, Denver and Dallas, but ultimately selected Dulles because it was more convenient to transport planes already stored there and in Maryland, especially the space shuttle that is now in a Dulles hangar.

About 3.5 million annual visitors are expected at the the annex off Route 50 near the Route 28 interchange in Fairfax County. In comparison, 9 million visitors are logged annually at the Mall museum, the most popular in the world, according to the Smithsonian.

The commonwealth of Virginia will fund a shuttle bus from the downtown museum to the Udvar-Hazy center at Dulles, and the Metropolitan Washington Airports Authority plans a shuttle for Dulles passengers who check in early and want a quick visit to the museum.

"This is special for me because my dad was a crew member on a B-24 bomber over China and Burma during the second World War," said Robert Daniels, executive vice president of Hensel Phelps, the construction company completing the project.

The annex, on 176 acres at Dulles International Airport, is scheduled to open in December 2003.John R. Dailey, director of the National Air and Space Museum, says the aircraft in the museum annex at Dulles International Airport will appeal to more than "airplane nuts."