Hopes to be the first balloonists to make a nonstop voyage around the world were dashed Wednesday for the three crewmen of a British balloon when its loss of lift forced them to land in the Sahara after less than a day aloft.

When they began to lose altitude, the crew members tried to maintain height by throwing out ballast and then heavy objects, but to no avail. When the crew tried to jettison an external fuel tank they found it had jammed, and one of them, Alex Ritchie, wearing a parachute, climbed outside the crew capsule and freed the tank.

“We owe a debt of gratitude to Alex,” Richard Branson, the captain of the team, said after the balloon landed in the Algerian desert. “He saved our lives.” Branson, 46, is chairman of the Virgin Group of Cos., which owns Virgin Airways.

None of the crew members were injured in the landing, and the valuable crew capsule, packed with expensive equipment, escaped serious damage. The project director for the flight, Michael Kendrick, said in London that the cause of the failure had not been determined.