The 3.4-mile, early-morning trip aboard the massive crawler-transporter took under seven hours from when the shuttle left the Vehicle Assembly Building to when it was secured at the launch pad.
The last time Atlantis made that trip was in February. The shuttle was on its launch pad when a freak hail storm swept through and pounded fuel tank with golf ball-sized hail that left thousands of dings in the tank's insulating foam.
• Click here to visit FOXNews.com's Space Center.
NASA managers postponed a planned mid-March launch and ordered the shuttle returned to the Vehicle Assembly Building for repairs. Technicians sprayed on new insulation foam in some areas, hand-poured foam on other areas and sanded down spots.
When the shuttle rolled out Tuesday, the orange tank had hundreds of white speckles at the top showing their work.
The launch is now planned for no earlier than June 8. A final decision will be made at the end of the month.
"It's a real success story — almost bordering on an Apollo 13-type story to develop that in such a short time," John Chapman, NASA's manager of the external tank project, said last week, referring to the engineering ingenuity that delivered the moon-bound crew safely back to Earth in 1970 after an oxygen tank ruptured on the spacecraft.
Foam debris coming off the external fuel tank has been of special concern to NASA since the seven astronauts aboard Columbia perished when a piece of foam from the tank struck a wing during launch, allowing fiery gases to penetrate the space shuttle while returning to Earth.
Until the shuttle arrives, Williams and her colleagues at the space station will make do with 2½ tons of fuel, air, water and other supplies that were delivered Tuesday by a Russian cargo vehicle.
NASA managers hope Atlantis' launch puts the space agency back on a regular schedule of shuttle missions after a five-month hiatus. The last space shuttle flight was in December, and three more missions are scheduled for this year after Atlantis.
The space agency has at least 14 more missions to finish building the space station and repair the Hubble Space Telescope before the shuttle fleet is grounded in 2010.
The next-generation spacecraft, Orion, isn't scheduled to fly astronauts until 2015.
Last week, leaders of almost two dozen aerospace companies sent a letter to members of Congress urging them to support funding NASA an additional $1.4 billion above the administration's 2008 budget request of $17.3 billion to narrow the gap when the United States won't have manned spaceflights.
"Future U.S. leadership in space is at stake," the letter said.