(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 filled Atlantis' tank in the pre-dawn hours.
Mission managers acknowledged it might seem foolish to proceed with fueling, given the dismal forecast, NASA spokesman Allard Beutel said. They said they would take another look at the forecast and decide whether it makes sense to keep counting down.
The four shuttle astronauts suited up after sunrise despite the still-iffy launch prospects.
"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.
Among the expected VIPs: 14 members of Congress, Joint Chiefs of Staff Chairman Adm. Mike Mullen, four members of the Kennedy family, two former NASA administrators, singers Jimmy Buffett and Gloria Estefan, and the first shuttle pilot of them all, Robert Crippen.
By 6 a.m., cars and RV were packed into almost every available space along U.S. 1 in Titusville, with cameras already trained on the launch pad in the hazy clouds across the Indian River. Many had planted chairs and staked out viewing locations just feet from the water. Some were still cocooned in sleeping bags as the sun rose.
Kenneth Cox, 25, an airport employee from Danville, Ind., joined three friends at the riverside. Hauling Lucky Charms, fixings for s'mores and a bottle of champagne to celebrate the launch, they slept off and on as the sun rose.
"It's the closing chapter of 30 years," said Cox, who went to Space Camp when he was in the fifth grade and has been enamored with the shuttle program as long as he could remember.
"I definitely think it's a somber attitude out here, because it's the last one," said Cox's friend, Simon Lin, 26, who works at Walt Disney World in Orlando. "It's brought so much to the tourist industry in Florida, and that's what we are. Closing it down, it's going to be sad."
Cherie Cabrera, 23, a Disney World employee, tried to explain the attraction.
"It's just powerful," she said. "There are so few people who have the ability to go to space, and for all of us to be here on the river, watching it launch and feeling it rise and feeling the wind, you feel like you're a part of it. You feel connected."
John and Jennifer Cardwell came from Fairhope, Ala., for their third attempt to see the shuttle launch. Twice before they made the trip only to have a flight canceled and they weren't able to stay. They brought their sons, Isaac, 6, and 3-year-old Eli.
"This is our last-ditch chance to see one," said 38-year-old Jennifer Cardwell, cradling a sleepy Eli in her arms just after dawn. "This is the end of an era, and I wanted to be able to experience it. My son is interested in space and science, and I wanted to encourage that.
"It's that last frontier, that last place left for us to explore," she said. "We've gone all over the world, and this is what's left."
NASA must launch Atlantis by Sunday or Monday or 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.
Explore further: Countdown begins for shuttle Atlantis' last flight