A tour bus drives by a launch countdown sign inside the NASA Kennedy Space Center on Wednesday, July 6, 2011 in Cape Canaveral, Fla. Space shuttle Atlantis is set to liftoff Friday, July 8, on the final flight of the shuttle program, STS-135, a 12-day mission to the International Space Station.
A tour bus drives by a launch countdown sign inside the NASA Kennedy Space Center on Wednesday, July 6, 2011 in Cape Canaveral, Fla. Space shuttle Atlantis is set to liftoff Friday, July 8, on the final flight of the shuttle program, STS-135, a 12-day mission to the International Space Station.Image Credit: NASA/Bill Ingalls