Artist's rendering of the balloon INTERACTIVE Layers of the atmosphere RELATED AUDIO Pilot Dave Liniger talks about the flight 'Including today, we're down to five days ...' 374 K / 13 sec. AIFF or WAV sound 'We're really optimistic ...' 249 K / 08 sec. AIFF or WAV sound

ALICE SPRINGS, Australia (CNN) -- A bold round-the-world balloon attempt delayed for two weeks by wind was put off again on Tuesday, this time because of rain showers over mission control in outback Australia. The 40-story balloon is designed to fly 39 km (24 miles) above the Earth, the highest altitude ever attempted in a manned balloon, and beyond the vagaries of the weather.

However, inclement weather close to Earth and technical problems have forced Team Re/Max to delay takeoff several times since their initial launch date of December 27.

The two crew members, American real estate tycoon Dave Liniger and Australian balloonist John Wallington, hope to become the first people to circle the globe non-stop in a balloon.

Originally, the balloon was to have had a three-man crew, but American Bob Martin opted out after it was determined that the balloon's gondola could not carry more than two people and reach the high altitude that flight plans called for.

The crew hopes to pick up stratospheric winds to carry them over the Southern Hemisphere during what they predict will be a 16- to 18-day journey.

The crewmembers will travel inside a pressurized gondola and be outfitted with Russian space suits.

"We'll actually wear the suits on the way up," Liniger said. "Well make sure we're stabilized and the temperature of the capsule is OK. Then we'll take them off and save them for an emergency -- some sort of pressure leak -- and then we'll be wearing them on the way down."

The Re/Max crew has admitted that the high-altitude flight is a risky venture, as the technology has not yet been tested.

"It's a bit more dangerous," Liniger said. "Low-level pilots have the ability to descend before they get into trouble. But we have a great deal of confidence in our crew and our craft."

The pilots say a Northern Hemisphere launch in June will be considered although political obstacles in China pose serious problems.

Beijing has closed its airspace to balloons after British tycoon Richard Branson strayed into a no-fly zone over Tibet on his recent failed attempt to make aviation history.