Thunderstorms forced NASA to call off Sunday evening's launch of shuttle Endeavour, the fourth delay for the space station construction mission.
The launch team came within minutes of sending Endeavour and seven astronauts to the international space station. But storms quickly moved in from the west and violated NASA's safety rules, and managers halted the countdown. They will try again Monday, despite an outlook calling for more bad weather.
"We got the vehicle ready, and the weather unfortunately did not cooperate with us today," launch director Pete Nickolenko told the seven astronauts aboard Endeavour.
"We understand and we'll be ready," replied commander Mark Polansky.
NASA has until Tuesday, possibly Wednesday, to launch Endeavour with the final piece of Japan's space station lab. Otherwise, it will have to wait until the end of July because of a Russian supply ship that's awaiting liftoff.
The three previous countdowns never made it this far.
Saturday's launch attempt was foiled by a series of lightning strikes around the pad that required extra checks of the many critical shuttle systems. Back in June, hydrogen gas leaks held everything up.
No leaks popped up this time, thanks to all of the repairs, as NASA fueled Endeavour's external tank for an early evening liftoff. The tight plumbing allowed Polansky and his crew to board the shuttle for the first time for a real launch try.
Endeavour holds the third and final segment of Japan's enormous $1 billion space station lab, named Kibo, or Hope. It's a porch for experiments that need to be exposed to the vacuum of space. The shuttle also is loaded with large spare parts for the space station and hundreds of pounds of food for the six station residents.
When the shuttle astronauts finally arrive at the space station, they will make up the biggest crowd ever in a single place in orbit: 13 people.
All of the major space station partners will be represented: the United States, Russia, Canada, Europe and Japan.
Endeavour will spend nearly two weeks at the space station. In all, the flight will last 16 days. Five spacewalks are planned to hook up the Japanese lab's new porch, replace space station batteries and perform other maintenance.
Eight shuttle flights remain, including this one, before NASA retires the fleet. All involve space station work.