Adventurer Steve Fossett has postponed his three-day non-stop flight around the world because of mechanical problems and poor wind conditions.
His Virgin GlobalFlyer plane was set to take off from the space shuttle runway in Florida, but the American stood down his team just before 1200GMT.
Engineers were concerned about unfavourable tail winds but they also found a leak in the fuel system.
The 61 year old is attempting to make the longest non-stop flight in history.
His journey will take him around the world once and across the Atlantic twice, landing in Kent, UK. If he makes it, he will eclipse a record set by Dick Rutan and Jeana Yeager in 1986.
Steve Fossett is expected to have another go at launching GlobalFlyer from the Kennedy Space Center on Wednesday.
Wrong wind
"We have a mechanical problem with a fuel leak and we cannot go with that," the millionaire told reporters who had gathered to watch the early morning take-off. "This is disappointing."
Tuesday's postponement was put down to a problem in the aeroplane's new fuel vent system. This has been upgraded to prevent a repeat of the leaks GlobalFlyer encountered on its climb to altitude during last year's mission.
That flight saw Steve Fossett become the first person to fly solo, non-stop around the globe without refuelling.
Even with the take-off losses, the plane had considerable reserves of fuel on landing and this convinced the adventurer he could push GlobalFlyer further before retiring the experimental aircraft to the Smithsonian National Air and Space Museum.
If Tuesday's mechanical problems had not occurred, engineers said GlobalFlyer could still not have taken to the 15,000-ft-long (4,600m) shuttle runway because of a tail wind.
To get its great bulk of fuel airborne, the vehicle must roll into a head wind.
VIRGIN ATLANTIC GLOBAL FLYER - LONG-DISTANCE JET PLANE
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