"We did not shift the date. We are still looking to fly in this large opening window starting on March 6 and ending on the 18th of April," Michael Kostelnik, NASA official in charge of the International Space Station and the space shuttle program, said in a telephone press conference.

"This is still our best window to fly," he said. "We have a lot of tests and evaluations that we're still waiting on."

NASA decided last February to put off resuming the shuttle flights in order to effect shuttle modifications deemed necessary.

Resumption of the flights had previously been slated for next September or October.

After the shuttle Columbia disintegrated on re-entry, an investigating commission issued a report highly critical of NASA's safety procedures in force since the shuttle Challenger exploded on takeoff in 1986.

SPACE.WIRE