After waiting two days for weather to clear, the specially modified carrier jet sped down the shuttle's runway shortly after dawn on Wednesday, the first leg of a planned three-day trek to the west coast.

"There's sadness to it go, but the space shuttle program had to end for us to move on to the next thing," said astronaut Greg Chamitoff.

NASA retired its three-ship fleet last year after completing the U.S. portion of the $100 billion International Space Station, a permanently staffed research complex that flies about 250 miles above Earth.

The agency is developing a new spaceship and rocket that can fly astronauts to the moon, asteroids and eventually to Mars. Russia now flies NASA astronauts to the station, at a cost of more than $65 million a seat. NASA hopes to buy rides from commercial companies beginning in 2017.

Endeavour was built as a replacement ship for Challenger, the shuttle lost in a 1986 launch accident that killed seven astronauts. It went on to fly 25 missions, including 12 to build and outfit the space station.

It flew the first assembly mission, carrying up the Unity connecting node, which was attached to the Russian Zarya base module.

"It's hard to believe it was 14 years ago," said Kenendy Space Center Director Bob Cabana, a former astronaut who commanded NASA's first station assembly flight in 1998.

Endeavour is the second of NASA's three surviving shuttles to be sent to a museum. Discovery, NASA's oldest surviving shuttle, is now on display at the Smithsonian Institution's Steven F. Udvar-Hazy Center outside Washington.

Atlantis, which flew NASA's 135th and final shuttle mission in July 2011, will be towed down the road to the Kennedy Space Center Visitor Complex in November.

NASA lost a fourth shuttle, Columbia, in another fatal accident in 2003. That shuttle as not replaced.

Endeavour will be headed to the California Science Center in Los Angeles.

(Editing by Jane Sutton and Doina Chiacu)

• A Permanent Economic Emergency