Indonesia intensified the search Sunday for a jetliner that disappeared with 102 people aboard last week, adding hundreds of soldiers and six helicopters to the mission.

More helicopters and a U.S. Navy ship were set to join the effort Monday.

Nearly 3,000 soldiers, police and civilians have been searching for the wreckage in dense jungles, while sonar-equipped ships and planes have scoured the seas. But there has been no trace of the Boeing 737 since it disappeared Jan. 1.

Nearly 700 more troops were sent Sunday to areas along Sulawesi island's west coast, said military spokesman Capt. Mulyadi, who uses a single name.

The pilot of Adam Air Flight KI-574 had reported 80 mph winds near the town of Majene on Sulawesi's coast just before the plane vanished from radar. But he did not issue a mayday or report technical trouble.

The plane had left Java island for the North Sulawesi provincial capital of Manado. It changed course twice due to severe wind and storms, said Eddy Suyanto, head of the search and rescue mission.

The flight lost contact over Majene halfway into the two-hour trip. No emergency location signal has been detected.

Several relatives of the passengers were invited to fly on Indonesian surveillance aircraft Sunday for a firsthand look at the search.

"I saw only dense jungles, deep ravines and steep mountains ... I'm pessimistic," said Fani Duran, whose sister and 18-month-old nephew had been on the plane.

A U.S. National Transportation Safety Board team arrived to help in the investigation Saturday, along with representatives from Boeing, the Federal Aviation Administration and General Electric. An Oregon man and his three daughters were among the passengers.

Singapore has been helping with aerial surveys.

The U.S. Navy's USNS Mary Sears Oceanographic survey ship was set to join the search Monday, said U.S. Embassy official Shannon Quinn.