BY late afternoon today another aviation milestone will have been reached, the non-stop circumnavigation of the globe in a balloon. All going well, pilots Bertrand Piccard and Brian Jones will cross nine degrees 27 minutes longitude west, high above Mauritania, the line which marks the completion of their 20-day trip around the world.
Last night they continued to make progress aboard the ninetonne Breitling Orbiter 3 on their final headlong rush across the Atlantic, riding high altitude winds at 36,000 feet and sailing along at about 90 m.p.h. Their Geneva headquarters predicted that they would cross over the African coastline at about midday and five hours later break the invisible marker that delineates a remarkable achievement.
A balloon circumnavigation has for decades represented the final great challenge for hot-air enthusiasts. It doesn't really matter that the achievement was made possible only with the help of lots of money, advanced technology, satellites and careful diplomacy - if the Swiss and British pilots cross that line they will go down in the history books.
They will have beaten a collection of serious competitors, including the businessman, Virgin's Richard Branson, who only last December ditched this own most recent round-the-world attempt in the sea. He congratulated the two adventurers yesterday and said that he would probably abandon plans for his fifth round-the-world attempt, which would have set out from Argentina next month.
And on March 7th the most immediate threat to Breitling's bid for the record, the competing British Cable and Wireless balloon, ditched in the sea off Japan. The balloon had left Europe 10 days before Piccard and Jones and could well have snatched victory from Breitling.
Yesterday morning the Anglo-Swiss pair beat the balloon endurance record of more than 17 days set by the crew of the Cable and Wireless balloon.
Bertrand Piccard, from Switzerland, and Brian Jones began their journey on March 1st, launching from the Swiss alpine village of Chateau d'Oex. Although leaving later than the Cable and Wireless crew, their great advantage as a Swiss-registered craft was permission to fly over China, an opportunity denied their British competitors.
This, they said, allowed them to carry less fuel and supplies and fly with a lighter, faster balloon. They enjoyed a relatively trouble-free flight for such ventures, with only the occasional need to climb out of their pressurised capsule to break heavy icicles off of their balloon canopy as Dr Piccard did on March 4th.
The pilots and their control centre acknowledged both the physical demands of controlling the balloon and the psychological pressures associated with the cramped on-board conditions and life on the edge.
They suffered an arduous six hours on, six off regime as they made their journey, and a particular toll was taken while crossing the Pacific Ocean. Dr Piccard, a psychiatrist, succumbed to the stress last Wednesday as the craft passed over Belize, resorting to hypnosis via satellite by a doctor in Belgium to overcome his problem.
All this will be quickly forgotten however if they achieve their goal and pass the magic line over Mauritania. The key now is the amount of fuel remaining. If supplies permit, the balloonists aim to touch down in Egypt tomorrow afternoon, 21 days after take-off.
If supplies run short they will land instead earlier tomorrow in either eastern Mauritania or Mali. The two will not land in the dark and instead will hover in place until their support teams can reach them.
"There is absolutely only one way to fail in this flight, and that would be to quit now," Dr Piccard told controllers yesterday. "We're both of the opinion, Brian and I, that we seem to have enough fuel to do it in accordance with the weather our specialists have forecast."
In just a few hours the quality of those predictions will be known.