The space shuttle Discovery capped a successful construction mission with a smooth landing in Florida on Wednesday, ending a 27-year flying career for Nasa's most-traveled spaceship as the agency faces an uncertain future.

Discovery commander Steven Lindsey circled his ship through clear, sunny skies over the Kennedy Space Center to burn off speed, then bee-lined toward the marsh-surrounded runway a few miles from where the shuttle blasted off for its final space flight on Feb. 24.

Discovery touched down at 11:57 a.m. EST (1657 GMT) to wrap up a cargo run and construction mission at the International Space Station. The shuttle accumulated 365 days in orbit over 39 missions, racking up more than 148 million miles (238 million km).

It will now be prepared for display at the Smithsonian National Air and Space Museum.

"Houston, Discovery. For the final time, wheels stop," Lindsey radioed to Mission Control in Houston, as the shuttle came to a standstill on the runway.

"Great job by you and your crew," replied astronaut Charlie Hobaugh from Mission Control.

"That was an awesome mission that you all had. You were able to take Discovery up to a full 365 days of actual time on orbit. I think that you'd call that a fleet leader, and a leader of any manned vehicle for time in orbit. So, job well done," Hobaugh said.

The US is ending the 30-year-old shuttle program because of its high operating costs to free up funds to begin work on new spaceships that can travel to the moon, asteroids and other destinations beyond the space station's 220-mile-high (350-km-high) orbit. Congress has, however, not yet allocated funds to start new programs.

"It's a pretty bittersweet moment for all of us," Lindsey said after landing. "As the minutes pass, I'm getting sadder and sadder about this being the last flight."

Sister ships Endeavour and Atlantis will have their finales in April and June, respectively, delivering the $2 billion Alpha Magnetic Spectrometer particle detector and a year's worth of supplies to the station.

The $100 billion research station is a project of 16 nations and has been under construction since 1998.

During its final mission, Discovery delivered a combination storage room-research lab to the station, as well as an external platform to house large spare parts.

It also carried tons of supplies and science gear, including a prototype humanoid robot built in partnership with General Motors.

Astronauts Stephen Bowen and Alvin Drew made two spacewalks to help prepare the station for operations after shuttle retirement. Nasa has turned over station crew transport to the Russians, though it hopes US commercial companies will develop space taxis so it can obtain flight services domestically.

Already two firms, Space Exploration Technologies and Orbital Sciences Corp, have Nasa contracts to ferry cargo to the outpost. Russia, Europe and Japan currently fly freighters to the station, though none can carry nearly as much as the shuttle.

Discovery is Nasa's oldest surviving spaceship. Two shuttles, Challenger and Columbia, were lost in accidents in 1986 and 2003, killing a total of 14 astronauts.

Discovery became the de facto fleet leader, flying both of Nasa's return-to-flight missions after the accidents. It now will lead the fleet into retirement.

A decision about where Endeavour and Atlantis will be displayed is expected next month.

In addition to Lindsey, Bowen and Drew, the last shuttle Discovery crew included pilot Eric Boe and astronauts Nicole Stott and Michael Barratt. – Reuters