Fewer Visit the Air and Space Museum

Tom Patterson, center, and Allen Witt, both of Iowa, try to figure out where the camera was that filmed the first steps on the moon during a visit to the National Air and Space Museum in Washington on Wednesday, Feb. 14, 2007. "I don't think this museum will ever lose its relevance," says Witt, "they could update some of the displays though." Officials are unsure what caused a drop in the huge crowd that the museum used to see.(AP Photo/Jacquelyn Martin)

(AP) -- It's a mystery even for researchers at the Smithsonian Institution: What happened to the huge crowds at the National Air and Space Museum? The estimated number of visitors to the museum plunged to about 5 million in 2006 from a six-year high of 9.4 million in 2003, according to the latest attendance report from the museum complex. And the decline has been far sharper than that of the overall Smithsonian, which includes 18 museums and the National Zoo.