CAPE CANAVERAL, Fla. - The countdown is under way for the last space shuttle launch.
But forecasters say it could be delayed. A shuttle weather officer says there's a 60 percent chance that rain or thunderstorms will postpone Friday's liftoff of Atlantis.
After that, the weather improves with each passing day.
The four astronauts assigned to the 12-day flight arrived at Kennedy Space Center yesterday.
Atlantis is making one final supply run to the International Space Station before retiring. As many as a million spectators are expected to jam the Cape Canaveral area for the historic send-off.