After the possibility of a delay due to bad weather the Atlantis space shuttle, with four astronauts on board, blasted off this afternoon at Cape Canaveral, Florida. The historic event was watched by an estimated one million spectators including 150 Irish Twitter users invited by NASA.

The launch, the last of the 30-year shuttle program, was delayed by just two minutes with the giant clock at the Kennedy Space Center stuck at 0.31. The delay was to verify that the launch pad support equipment was retracted all the way.

It will now be at least three years, possibly five or more, before astronauts launch from US soil. The Atlantis shuttle mission is the 135th mission to take place as part of the 30-year NASA program. The crew above the Atlantis will deliver a year's worth of critical supplies to the International Space Station and return with as much garbage from the Station as possible.

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It's estimated that tens of millions of people across the world watched the launch on TV. The shuttle was airborne and visible for 42 seconds before it disappeared into the clouds, according to Daily Mail reports.

Among the lucky people on the ground were 150 Twitter users from Ireland selected at random by NASA. Ruth McAvinia (@ruthie147), a journalist and broadcaster from Ireland, was among the guests.

She tweeted:

"All sorts of emotions round Kennedy Space Center right now. Historic day"

" i'm pretty much speechless (sic)"

"Time of life."

The crew onboard the Atlantis shuttle are Chris Ferguson, Pilot Doug Hurley, Mission Specialist Sandy Magnus and Mission Specialist Rex Walheim. As the shuttle took off Mike Leinbach, the launch director said "For the final time, good luck, godspeed, and have a little fun up there"

After the launch of the final space shuttle, NASA Chief, Charles Bolden posted a video message saluting the final flight and offering some hope for the future of US spaceflight.

"Over three decades, the shuttle has brought this nation many firsts, and many, many proud moments," Bolden said, according to Fox News reports. "The shuttle pioneers have made the next chapter of human spaceflight possible."

"American ingenuity is alive and well, and it will fire up our economy -- and help us win the future." he added.