NASA officials said Tuesday shuttle Discovery had an opportunity to land three sites, after a day delay because of bad cloudy weather. The shuttle crew are planned to return home Tuesday.
Nasa hopes to bring the shuttle down at 1007 BST (0507 EST; 0907 GMT) at the Kennedy Space Center in Florida. If the weather remains a problem in Florida, the shuttle could land at air bases in California or New Mexico.
The U.S. space agency's administrator Dr Mike Griffin said there was "no agony" over the delay.
"We're going to land one way or another, one place or another, and all we're talking about is where," Dr Griffin was quoted as saying by BBC.
Mike Fincke, an astronaut who spent six months in space on the international space station, told CNN that Collins wouldn't have had much time to see the runway clearly.
"Eileen Collins is an experienced test pilot, and she'd be able to land almost blindfolded. But there's no reason to take that risk," he said.
"This morning we thought there might be a cloud deck of about 500 feet, and that would have obscured the runway."
Mark Polansky, a pilot during a 2001 mission aboard the shuttle Atlantis, said the waiting is easier for orbiting crew members than it is for their families.
"It's much harder for people on the ground," Polansky said. "Loved ones don't know when their people are coming home."
Polansky and astronaut Nicholas Patrick are assigned to a shuttle mission aboard Discovery in 2006. Patrick said the orbiting astronauts have more than enough supplies, CNN reports.
It was during re-entry in February 2003 that Columbia broke apart, killing its seven crew members.
Investigators later determined that super-heated gases that normally surround the orbiter as it returns to Earth entered Columbia's left wing through a hole created when insulating foam fell from the shuttle's fuel tank and struck the vehicle during launch.
The Columbia break-up left a trail of debris across Texas and Louisiana and resulted in vows from NASA that tighter safety precautions would be taken on future trips - and that the problem of falling foam would be solved.
Discovery's two-week mission included spacewalks where astronauts inspected the spacecraft for damage for the first time and removed potentially dangerous material from the bottom of the ship, Bloomberg reminds.
A board that investigated Columbia's destruction had recommended that NASA find ways to examine and fix the spacecraft in orbit to prevent future accidents.
Cameras installed on Discovery captured pieces of insulating foam falling from the shuttle's external fuel tank during takeoff on July 26, the same problem that led to Columbia's destruction, and engineers also spotted a damaged insulation blanket during inspections of the spacecraft.
Engineers determined the foam didn't hit Discovery, and said the damaged blanket shouldn't cause any problems on the ship's return. Astronaut Steve Robinson conducted the first spacewalk under the vehicle in the history of the shuttle program to remove pieces of cloth that managers were afraid would overheat on the shuttle's voyage home.
Photo by BBC.