The five astronauts aboard the space shuttle Atlantis were kept in orbit by bad weather at their Kennedy Space Center landing strip in Florida for the second day.
As dark clouds marched up the Florida peninsula and 19-knot gusts swept the shuttle's 3-mile-long (5-km) landing strip, NASA determined the threat of rain and crosswinds would make a landing unsafe.
Although the weather is supposed to improve tomorrow, the space agency is taking no chances, opening two additional landing strips in Edwards, California and White Sands, New Mexico.
The shuttle has only enough cryogenic fuel to power it until Wednesday, but NASA also has several other landing strips around the world that could be activated in an emergency.
For the crew, the extra days meant more time looking out of windows as the blue-white Earth scrolled beneath them and the stars hung above.
But the first order of business was to reconfigure the shuttle systems for another day in space.
High winds were also to blame yesterday, when Atlantis had been scheduled to end a mission to the International Space Station that saw the five-astronauts deliver and install a $1.4 billion laboratory module.
This flight also featured the 100th US spacewalk since astronaut Ed White became the first American to float outside a spacecraft in 1965, about three months after the Russians first accomplished the feat.