Friday, November 27, 1998 Published at 17:33 GMT
The driving force
It is freezing cold in an unpressurized capsule at 18,000 ft and you have to be constantly on the alert for changes in weather, so the crew gets little sleep.
There is even the risk of being shot down - in 1995 the balloon of two Americans was shot down and they were killed when they entered Belorussian airspace.
So what drives them? Money? Richard Branson and Steve Fossett are already millionaires.
A place in the history books? Or, perhaps, the simple pleasure of floating away and above it all?
Branson described his fascination with this gentle sport: "There were definitely times where I said to myself, if I get out of this alive I will definitely thank someone for getting me out of this fix, and call it a day.
"Then about three hours later you start seeing the magnificence of the Sahara and the beautiful mountains, the dawn coming up, being somewhere which most people in the world have never seen... It's difficult to resist the whole fascination of that." In the last year three men have nearly lost their lives trying to fly round the world in a balloon.
The winner of this exclusive race could win up to $1.5 million (£919,664).
The US brewery Anheuser-Bush has set aside a one million-dollar prize: $500,000 (£307,000) go to the winners, and a further $500,000 to the charity of their choice.
But most of these men are millionaires already, so it can't be the money that drives them on.
One can only assume that the challenge and the hope of glory keeps the competition running.
Rules of the game
The deadline for the great ballooning challenge is December 31, 1999. The International Aviation Federation, which officiates over record-breaking flights, has set strict rules: