The U.S. space shuttle Atlantis has landed in Florida after a construction visit to the International Space Station. The shuttle crew added equipment that will support future research laboratories.

Atlantis ended 11 days in orbit, touching down on schedule at the Kennedy Space Center.

The shuttle spent six of those days at the International Space Station, where astronauts mounted the first segment of a backbone across the U.S. laboratory. It is a 13-ton girder that will eventually reach 107 meters and support huge solar panels and other equipment for future European and Japanese lab modules.

The crew also inaugurated the first space railway, a small remotely-operated flatcar that will roll along the beam carrying the station's crane for later assembly activities.

The next shuttle flight in early June will exchange space station crews and haul up a platform for the space trolley to carry the crane.