The space shuttle Challenger remained locked on its launching pad Saturday, three months behind schedule.
The spaceship, which is being readied for a March liftoff with two communications satellites and a crew of seven that includes Sen. Jake Garn (R-Utah) and a French astronaut, was transported to the pad atop a giant tracked vehicle late Friday.
It had been delayed more than nine hours in an assembly hangar while technicians fixed a gas leak in a fuel tank pressurization system.
That followed a 24-hour delay of the move on Thursday to replace a faulty electronic component in a booster rocket.
Sources said the delays may cause a one-day postponement in the liftoff, to March 4. Its original December flight date was reassigned to sister ship Discovery when tiles had to be removed and rebonded.
The crew members will climb aboard Challenger today to take part in the final two hours of a practice countdown.
The National Aeronautics and Space Administration also announced that Robert L. Crippen will command the first shuttle launched from Vandenberg Air Force Base, Calif., next year.