The region also lacks roads to reach areas on the ground and communications infrastructure is often poor.
 
Captain Mulyadi, a spokesman for the Indonesian military, said in Makassar on Monday: "We hope the involvement of the [US] oceanographic survey ship Mary Sears will boost the search effort."
 
He said Monday’s search and rescue mission would focus on the Bone Strait between the two southern arms of Sulawesi island and the onshore areas of western Sulawesi.
 
In addition to the US vessel and local helicopters, an American military jet, a Singapore air force Fokker-50 and other Indonesian military jets are already helping the search.
 
On Sunday, waiting relatives confronted Jusuf Kalla, the Indonesian vice-president, in Makassar, demanding the authorities do more and also accept more foreign help.
 
The vice-president told them the government would spare no effort in the search.
 
"I won’t go home until they find the plane. This uncertainty makes us confused,"  said Hendra Tuna, whose niece and her husband were among the passengers.
 
According to the Indonesian authorities, the Boeing 737 aircraft operated by budget airline Adam Air had altered course twice before disappearing from the radar on New Year’s Day near the Sulawesi coastal town of Majene, without issuing any distress signal.