BEIJING, Dec. 29 -- An AirAsia passenger plane that went missing with 162 people on board is likely at the bottom of the sea, Indonesian National Search and Rescue Agency chief said Monday.

"We assume the missing jet at the bottom of the sea based on the coordinates given to us and evaluation that the estimated crash position is in the sea," Bambang Soelistyo told media.

He added this was the preliminary suspicion and needs verification.

Of the 155 passengers on board the plane flying from Indonesia to Singapore, 149 are Indonesians.

Soelistyo said Indonesia did not have submersible vehicles and other equipment required to retrieve the plane from the seabed, but that it is reaching out to other countries for help if necessary.

"Due to the lack of technology that we have, I have coordinated with our foreign minister so we will borrow from other countries which have offered," he said.

On its way from Indonesia's Surabaya to Singapore, the AirAsia jetliner lost contact with ground control about 42 minutes after its takeoff at 5:35 a.m. Jakarta time on Sunday (2235 GMT Saturday).

AirAsia said the plane, which was on the submitted flight plan route, had requested to turn left and climb to 10,360 meters to avoid clouds before it disappeared from radar.

A search and rescue operation was launched Sunday involving Indonesia, Singapore and Malaysia near Bangka Belitung islands in the Java Sea over which the jetliner lost contact with ground control. The search was suspended at 5 p.m. Jakarta time on Sunday (1000 GMT) due to darkness.

The operation resumed earlier Monday as planes and helicopters have moved to the waters where the jetliner was believed to have lost, Ahmad Toha, staff at the Indonesian National Search and Rescue Agency, told Xinhua by phone.

"The agency has broadcast information to ships that were passing through the waters to join in monitoring the seas and asked them to report whether they found any signs of crash," said Toha.

The Indonesian army will conduct search on land around the scene where the plane was suspected to go missing, said Djoko Murjatmodjo, director general of air transport of Indonesian Transport Ministry.

Also on Monday, Singapore deployed another C-130 aircraft, the formidable-class frigate (RSS Supreme) and missile corvette (RSS Valour), to aid in the operation.

A Royal Australian Air Force AP-3C Orion also took off from the northern city of Darwin early Monday to help in the task, the Australian Defense Force said.

Australian Prime Minister Tony Abbott has called Indonesian President Joko Widodo, pledging assistance.

Meanwhile, South Korea said Monday that it plans to send a surveillance plane to join the Indonesia-led search for the missing plane.

China is ready to send aircraft and vessels to join the search and rescue work for missing AsiaAir flight QZ8501, Foreign Ministry spokeswoman Hua Chunying said in a statement on Monday.

China has told Indonesia that it is willing to provide other assistance as needed, Hua said.

AirAsia said Sunday night in a statement that its management had met with members of the families of those on board the missing plane to update them on the latest developments and reconfirmed their commitment to offering assistance.

"We are deeply shocked and saddened by this incident. We are cooperating with the relevant authorities to the fullest extent to determine the cause of this incident," said Sunu Widyatmoko, CEO of AirAsia Indonesia.

He also said the airline had already mobilized a support team to help the families, including accommodation and travel arrangements. A briefing center has also been set up in Surabaya for the families, he added.