Bad weather at two sites forced flight controllers to cancel all landing attempts Tuesday for space shuttle Endeavour, postponing for yet another day the return to Earth for the three men who spent a record six months aboard the international space station.

This was the second day in a row weather prevented Endeavour from returning to Earth.

Flight controllers canceled the first landing opportunity at the Kennedy Space Center in Florida because of thick clouds and showers.

But they held out hope the shuttle could land during the second and last attempt for Tuesday. However, the weather did not improve.

"We're disappointed," shuttle commander Kenneth Cockrell told Mission Control.

Monday's two landing times in Florida also were called off because of bad weather.

A backup landing site at Edwards Air Force Base in California was called up. But flight controllers decided Tuesday morning not to use it because of concerns about gusty wind around the base and improved forecasts on Wednesday for both the Florida and California landing sites.

The shuttle can stay in orbit until Thursday.

Space station Alpha's returning crew of U.S. astronauts Daniel Bursch and Carl Walz and their Russian commander, Yuri Onufrienko, logged their 195th day in orbit Tuesday. The Americans broke NASA's 188-day space endurance record last week.

Endeavour launched on June 5 to deliver a new three-member crew to Alpha and bring home the departing crew, which had been there since early December.

Bursch, Walz and Onufrienko did not expect to live on the space station for six months but Endeavour's flight was delayed by a month so the shuttle astronauts could train to repair Alpha's robot arm during a spacewalk. Then stormy weather and a leaky shuttle valve added another week's delay.