A jetliner carrying 102 people was forced to change course twice after encountering stormy weather over northern Indonesian waters, an official said, as the air force and navy widened their search Saturday for the missing Boeing 737.

A six-member U.S. National Transportation Safety Board team arrived on Sulawesi island to help investigate the apparent crash of Adam Air Flight KI-574, which vanished from radar screens Monday over the coastal town of Majene. Three Americans — a father and his two daughters — were on board.

"Whatever happened to the plane, it was likely rapid and catastrophic," said Patrick Smith, a U.S.-based airline pilot and aviation commentator, pointing to a possible massive structural failure due to metal fatigue or an onboard explosion.

He noted that in many accidents, "there are no distress calls simply because the cockpit crew is too busy dealing with the situation rather than calling around for help."

The plane left Indonesia's main island of Java for Manado on Sulawesi but altered course and turned westward halfway into the two-hour trip after being warned of rough weather near the city of Makassar, said Eddy Suyanto, head of the search and rescue mission.

But when it ran into winds of more than 130 kph (80 mph) over the Makassar Strait, it changed course again, bringing the plane eastward toward land, then lost contact, he said.

It is not clear why there were never any transmissions from the plane's emergency locator.

Smith speculated it may not have been operational or — in the event of a crash at sea — that it could have sank into an underwater trench from which its signals could not be picked up.

Nearly 3,000 soldiers, police and civilians have been trudging along steep jungle paths on Sulawesi, while sonar-equipped ships and a fleet of aircraft have scoured the sea over an area roughly the size of Ireland.

Saturday's aerial search was focusing on land and sea along 500 kilometers (300 miles) of coastline stretching from Palu city in the north to Makassar in the south, said Suyanto.

Three warships will also comb the Makassar Strait area, said Suparman, chief of Makassar Search and Rescue Agency, who goes by a single name.

Authorities wrongly said Tuesday the wreckage had been found with a dozen survivors, causing further anguish to relatives camped out at airports and hotels in Manado and Makassar.

Many family members have provided the disaster crisis center with medical records, photographs and other information that would be needed to help identify the dead.

"All we do is watch television," said Fandi, who had four relatives on the plane and like many Indonesians only uses a single name. "Officials from Adam Air aren't able to tell us anything."

Adam Air is one of about 30 budget carriers that sprang up in Indonesia after 1998 when the industry was deregulated. The rapid expansion has led to cheap flights to scores of destinations across Indonesia, but has also raised concerns about maintenance of the leased planes.

Air navigation can be difficult in Indonesia, which spans 6 percent of the equator, because there are gaps in the communications systems. Last year, an Adam Air Boeing 737 flew off course on a stretch of the same route and was lost for several hours before it made an emergency landing at a small airstrip, hundreds of kilometers (miles) off course.