WASHINGTON — Retired space shuttle Discovery streaked across the sky one last time Tuesday, piggybacking on a modified Boeing 747 jetliner to Washington Dulles International Airport as it headed for its final resting place: on display at the Smithsonian Institution.

“It’s a once-in-a-lifetime opportunity,” said Caroline Boucher, who was visiting from Bangor, Pa.

Tourists and locals gathered on the National Mall, on rooftops and at other sites around the nation’s capital to see the historic shuttle in flight before it goes on permanent display at the National Air and Space Museum’s Steven F. Udvar-Hazy Center in Chantilly, Va.

With more flights into space than any other craft, Discovery has circled Earth 5,628 times and carried 246 crew members to orbit. During a mission in 1998, one of those crew members was astronaut John Glenn, then 77 years old. The former senator — the first American to orbit Earth, in 1962 — became the oldest astronaut to fly into space.

The historical significance resonated for Lisa Percival of Seattle, who was in Washington on a one-day layover and staying three blocks from the Mall. Percival was in kindergarten when Glenn made his first voyage into space.

Percival walked from her hotel to watch Discovery as it passed behind the U.S. Capitol. “I had tears in my eyes and goose bumps,” she said. “I never dreamed I would see a sight like that.”

In 1990, Discovery deployed the Hubble telescope and played an integral role in the International Space Station’s development. The first Americans to return to space after the Challenger and Columbia disasters flew on the wings of Discovery. On March 9, 2011, the shuttle completed its 39th and final mission. It’s the first of the three active shuttles to be retired by NASA.