A Concorde jet with 100 Americans aboard lost a 9-foot piece of its tail Wednesday while attempting the aircraft's first supersonic circumnavigation of the globe, but it landed safely in Sydney.

"It wasn't till we got out of the plane and saw the fire trucks and all the press . . . that we knew something was wrong," said American journalist William Buckley Jr., who helped organize the trip, which cost each passenger $39,000.Part of the rudder disintegrated while the British Airways supersonic jet was flying at 40,000 feet at about 1,500 mph - nearly twice the speed of sound - from Christchurch, New Zealand, said Peter Stanton, an airline spokesman.

"It experienced a shudder while over the Tasman Sea that was thought to have been air turbulence," said Stanton.

He said the pilot was unaware of any problem until he was alerted by the control tower at Sydney's Kingsford-Smith International Airport.

But another passenger on the 1,000-mile flight, which lasted one hour and 25 minutes, said the plane shuddered and the passengers were tense.

Buckley said, "There is a possibility they (British Airways) will find a defect . . . that will result in the grounding of other Concordes. But obviously they're hoping that won't be so, that this is simply an eccentric fluke."

"It was a normal landing, there was no emergency," Stanton said. "The pilot, Capt. David Leney, was told by the control tower that a piece of the tail was missing." There were no injuries among the 100 passengers, all Americans, on the 38,343-mile journey that started April 1 in London.

Pat Boody, a British Airways airport service manager, said the cause of the tail problem was being investigated and that the plane would not be allowed to fly "unless it is absolutely safe."

Australian Associated Press said the Concorde was about 15 years old and apparently had never experienced any problems.

"I'm glad that it was a plane that could manage without that much superfluous tail," said Buckley.