CAPE CANAVERAL, Fla. (AP) —

NASA's final four shuttle astronauts boarded Atlantis for liftoff Friday on the last flight of the 30-year program, even as potential rainstorms threatened to delay the launch.

Forecasters stuck to their original 70 percent chance of bad weather, as the veteran crew climbed aboard the spacecraft. NASA was hopeful. "We do have a shot at this today," launch director Mike Leinbach assured his team. Commander Christopher Ferguson gave a thumbs up as he was strapped in after sunrise despite the still-iffy launch prospects. On his way to the spacecraft, Ferguson had jokingly beckoned for more applause, clapping his hands at one point. The astronauts posed for pictures before boarding. 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."