CAPE CANAVERAL, Fla. (AP) -- NASA fueled space shuttle Atlantis for liftoff Friday on the final flight of the 30-year program, even though stormy weather threatened to delay the launch.
Forecasters stuck to their original 70 percent chance of thunderstorms or rain, as fuel began flowing into Atlantis' tank in the pre-dawn hours.
Mission managers acknowledged it might seem silly to proceed with fueling, given the dismal forecast, NASA spokesman Allard Beutel said. They said they would reassess the weather at sunrise and decide whether it makes sense to keep counting down.
The four shuttle astronauts were still asleep when the tanking operation began.
"Have you done your rain dance for the day?" joked Aly Mendoza, the tank and booster rocket vehicle manager.
Atlantis holds a year's worth of supplies -- more than 8,000 pounds -- for the International Space Station.
An estimated 750,000 people are expected to jam Cape Canaveral and surrounding towns for this final shuttle launch, reminiscent of the crowds that gathered for the Apollo moon shots.
By late Thursday, dozens of RVs and other vehicles already had claimed prime viewing spots along the Banana River.
NASA must launch Atlantis by Sunday or Monday, otherwise it will have to wait until at least July 16 because of an unmanned rocket launch scheduled for next week.
The 12-day mission will close out the space shuttle program, which began with the launch of Columbia in 1981. Atlantis will join Discovery and Endeavour in retirement, so NASA can focus on sending astronauts to asteroids and Mars. Private companies will take over the business of getting space station cargo and crews to orbit.
Once Atlantis soars, it will be another three years -- possibly five or more -- before astronauts blast off again from U.S. soil.
This will be the 33rd flight for Atlantis and the 135th shuttle mission overall.
"Everybody should be really proud how we've ended and just finishing strong," Mendoza said.
(Copyright 2011 by The Associated Press. All Rights Reserved.)