After being moved from the Vehicle Assembly Building, space shuttle Endeavour rests on launch pad 39b at the Kennedy Space Center in Cape Canaveral, Fla., Wednesday, July 11, 2007. The launch is scheduled for Aug. 7. [AP]

It's been a nearly five-year wait for Endeavour, but the shuttle has nothing on Morgan: She's been waiting 22 years to reach orbit.

In 1985, Morgan was picked as Christa McAuliffe's backup to become the first teacher in space under a special NASA program. Then the Challenger carrying McAuliffe broke apart shortly after liftoff in 1986, and Morgan returned to teaching. In 1998, she was selected as a full-fledged astronaut.

On her first mission, the 55-year-old Morgan will operate the shuttle's robotic arm, coordinate the transfer of cargo and talk from space to students at three schools, if the mission is extended.

Talking to students and teachers Wednesday morning, Morgan said she was most looking forward to seeing McCall, Idaho ¡ª where she taught elementary students ¡ª from space. She said the Endeavour crew was training hard during their last few weeks before launch.

"There's a ton of work to be done," Morgan said during the forum at Johnson Space Center.

Morgan is far from being the oldest astronaut ever to fly on a space shuttle. Astronaut Story Musgrave was 61 when he flew his last mission aboard Columbia in 1996, and John Glenn was 77 when he flew aboard Discovery in 1998.

The Endeavour crew will deliver a new truss segment, 5,000 pounds of cargo and fix a gyroscope, which helps control the station's position. It also plans four spacewalks if the mission is extended to 14 days.

"It has a little bit of everything," said Matt Abbott, lead shuttle flight director.

Endeavour reached the launch pad shortly after 3 a.m., completing a 3.4-mile trip aboard the massive crawler-transporter from the Vehicle Assembly Building in seven hours. It was a day late because the weather had nixed plans to move it early Tuesday.

The launch would be NASA's second shuttle flight this year.

The last time Endeavour was at the pad was in November 2002, before its launch on a construction mission to the space station. It was the last shuttle flight before the Columbia disaster killed seven astronauts and grounded the space shuttle program for 2 1/2 years.

Endeavour has since undergone a major tune-up. The shuttle's structure was inspected for corrosion. Filter and seals were replaced. More than 1,900 thermal blankets were examined, and two windows were replaced with thicker panes.

"We're really excited to have Endeavour fly again," Kim Doering, NASA's deputy manager of the space shuttle program, said Tuesday. "Obviously, having brand new belts and hoses and having just checked the structure and replaced all the tiles ¡ª they're brand new ¡ª makes this a very nice vehicle to climb on to."

Endeavour also has a new system which allows power from the space station to be transferred to the shuttle while docked. If the new system works properly, the 11-day mission will be extended by an extra three days.