Space shuttle Atlantis STS-135 pilot Doug Hurley (R) talks with the media alongside commander Chris Ferguson after arriving at the Kennedy Space Center in Cape Canaveral, Florida July 4, 2011. [Photo/Agencies]

CAPE CANAVERAL, Florida - The four astronauts who will close out NASA's 30-year space shuttle program arrived Monday for their history-making launch week, saluting the nation's birthday and all those who contributed to Atlantis' final flight.

The launch countdown begins Tuesday. Liftoff is set for Friday at 11:26 am EDT (1626 GMT) before an estimated crowd of up to 1 million people.

Commander Christopher Ferguson and his crew received small American flags as launch director Mike Leinbach greeted them out on the runway. The four needed just two training jets for the flight from their training base in Houston.

"This is a day that's decidedly American, a day where we kind of reflect on our independence and all the wonderful things that we really have as a part of being United States of America," said Ferguson, a retired Navy captain.

"It's wonderful that you've all came out to join us," he told the approximately 65 photographers and other journalists who swarmed the runway. He urged them to go and enjoy some barbecue, fireworks and apple pie.

Altogether, about 2,500 members of the news media have requested credentials to cover the launch. As of Monday, the estimated total crowd count also had risen: NASA spokesman Allard Beutel said between 750,000 and 1 million people now are expected to jam the area to witness the end to shuttle history.

That's considerably more than the crowds that showed up for Discovery's last liftoff in February and Endeavour's in May. The Endeavour send-off even attracted President Barack Obama and his entire family, but a launch delay in late April had him mingling instead with the shuttle crew and Rep. Gabrielle Giffords, the wounded wife of commander Mark Kelly.

A busy 12-day flight lies ahead, Ferguson said, making note of the abridged crew. Atlantis will make a supply run to the International Space Station, before joining Discovery and Endeavour in retirement.

"When it's all over ... we'll be very proud to put the right-hand bookend on the space shuttle program," he said.

Added co-pilot Douglas Hurley: "We're so very proud to be here sharing our nation's birthday with you all and the folks here at Kennedy, and we just want to honor the entire Kennedy team that has worked on these magnificent machines over the last 30-plus years."

NASA hasn't launched so few shuttle astronauts since mission No 6 in 1983. That's because there are no more shuttles left to retrieve them from the space station in the event of serious launch damage to Atlantis; the shuttle crew would have to be rescued by Russia's much smaller Soyuz capsules.

Americans will continue to hitch rides aboard Soyuz spacecraft to and from the space station, until private companies are able to launch their own spacecraft with crews. That's at least three to five years away.

The Obama administration wants NASA to focus on expeditions to an asteroid and Mars, instead of repeated trips to low-Earth orbit. There's not enough money to do both, shuttle program manager John Shannon told reporters last week.

"We're sacrificing the shuttle to enable us to be able to take that next step," Shannon said. "If we were going to retire the shuttle, this is the time to do it," he said, noting that the space station is now completed and in good shape.

Despite the overriding significance of this last shuttle flight, astronaut Rex Walheim delighted in the little things Monday.

"It's such a pleasure to come down here when you have a rocket on the pad and it's got your stuff loaded on it," he said with a wide grin.

The three men - all with military backgrounds - are joined on the crew by Sandra Magnus, a civilian scientist. Each has flown in space before.