Balloonists from 12 countries are to gather in Bristol later this year to take part in one of the world's oldest aviation races.
To win, the 22 teams have to try to travel the greatest distance from the city in hydrogen-filled balloons.
The Duke of Edinburgh and Sir Richard Branson are patrons of the 54th Coupe Aeronautique Gordon Bennett race.
It will be the first time in its 104-year history that the international race will take off from the UK.
It comes after a British team won the contest in 2008.
David Hempleman-Adams, from Wiltshire, won the race then with co-pilot Jon Mason, giving them the honour of hosting it in their home country.
Mr Hempleman-Adams and Mr Mason were the first UK team to win, flying 1,098 miles (1,767km) from Albuquerque in New Mexico to Lake Michigan in just over three days.
The pilots in command of the British teams are David Hempleman-Adams, Colin Butter and Janet Folkes.
It is due to launch from Ashton Court - the site of the Bristol Balloon Fiesta - at dusk on 25 September.
The gas balloons are controlled by releasing gas to go down and throwing out sand to go up.
The pilots stand in small wicker baskets which are equipped with flight instruments, radios, food and warm clothing.
Sir Richard said: "The pilots will be airborne for three or four days without landing and, in seeking to fly the greatest distance, will go for thousands of miles crossing several countries.
"I know from some of my own long-distance balloon flights what a challenge and adventure this will be, and I will be watching the live tracking on the website with great interest."