Charles Lindbergh’s “Spirit of St. Louis” aircraft, bottom of frame, one of the premiere artifacts at the National Air and Space Museum, is seen on the ground floor of the museum, Thursday, Jan. 15, 2015, after being lowered for the first time in more than 20 years to have conservation work done and giving visitors a rare chance to see it up close in Washington. Lindbergh made the first trans-Atlantic flight and landed in Paris in 1927. (AP Photo/Jacquelyn Martin)

WASHINGTON - Charles Lindbergh's Spirit of St. Louis, one of the most treasured aircraft at the National Air and Space Museum, has been lowered to the floor for its first conservation treatment in 22 years.

For decades, the single-engine aircraft has been suspended from the ceiling and seen from afar. Early Thursday, it was carefully lowered to the floor. Now visitors are getting an up-close look at the historic plane and can better imagine what it must have been like to fly.

The Spirit of St. Louis "is a flying fuel tank" that carried 451 gallons of gas, said Curator Robert van der Linden. Two large fuel tanks take up the nose of the aircraft, leaving no room for a front windscreen for Lindbergh to see through. Instead he relied on side windows, a periscope and compass headings and calculations to carry out his 33 1/2-hour flight.

For the next eight months, the aircraft is expected to be in full view to the museum's millions of visitors as conservators repair cracks in its fabric skin and search for other damage. The lightweight fabric exterior, common for aircraft of the 1920s, has become dry and brittle with age. The fabric covers wooden wings and a fuselage made of steel tubing.

"Even though you can't touch it, you're a lot closer to it, and it somehow seems a lot more personal," said Van der Linden, chairman of the museum's aeronautics department.

Lindbergh became a hero of flight in 1927 when he made the first solo trans-Atlantic flight, flying nonstop from New York to Paris. When the 26-year-old pilot landed in Paris, a crowd of more than 100,000 was waiting to greet him. Many swarmed the aircraft, tearing off pieces for souvenirs. The French air force helped to quickly make repairs.

After the famous flight, Lindbergh flew across the United States on a celebratory tour and then on to Central America and South America. Small flag symbols were painted on the nose of the Spirit of St. Louis to represent each country he visited. The last flag is from Cuba, dated 1928.

Lindbergh presented the plane to the Smithsonian that same year, and it was displayed in the Arts and Industries Building on the National Mall as an international symbol of the advances in aviation technology.

The plane will eventually be hoisted again to its high perch in the museum's "Milestones of Flight" gallery, which is being reimagined to provide more stories about the people, politics and business behind aviation achievements.

"The airplane itself, the Spirit of St. Louis, is a very straightforward aircraft," Van der Linden said. "What made it special was the flight, the fact that Lindbergh by himself and at that time an unknown air mail pilot conquered the Atlantic."

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News from © The Associated Press, 2015