JAKARTA, Dec. 29 -- The search and rescue operation for a missing AirAsia plane expanded on Monday with more countries joining the sea and aerial search while an Indonesian official assumed that the ill-fated jetliner is likely at the bottom of the sea.

Indonesia's National Search and Rescue Agency told the media that the missing jet with 162 people on board is believed to have sunken into the bottom of the sea based on the coordinates given and evaluations.

"Because the coordinate that was given to us and the evolution from the calculation point of the flight track is at sea, our early conjecture is that the plane is at the bottom of the sea," said Bambang Sulistyo, head of Indonesia's national search and rescue agency.

Should the projection be true, Indonesia needs to cooperate with other countries to bring the wreckage to the surface, he added.

The Airbus A320-200 disappeared Sunday en route from Surabaya in Indonesia's east Java to Singapore after the pilot requested a change of flight plan due to stormy weather.

The flight lost contact with the ground after the air traffic control consented to the pilot's request to change flight route but it did not approve the request to raise its height to 34,000 feet (10,303 meters).

The aircraft, which sent no distress signal, must have run out its fuel if it kept flying. said Djoko Murjatmodjo, director general of air transport of Indonesian Transport Ministry.

Aircraft and ships from Singapore, Malaysia and Australia have been deployed to assist Indonesia's search efforts, which is centered on waters around the islands of Bangka and Belitung in the Java Sea across from Kalimantan on Borneo island.

Five aircraft have been sent to search for the plane, including two C-130 military transport aircraft and a Boeing 737, according to Indonesian air force.

The army has been combing the land where the plane was believed to go missing.

A Royal Australian Air Force AP-3C Orion equipped with sophisticated search equipment took off from the northern city of Darwin early Monday as Singapore deployed two Air Force C-130 aircraft and two warships to join the operation.

Malaysia has also dispatched three vessels and three planes for the hunt.

AirAsia, a Malaysia-based budget airline, said 155 of those on board flight QZ8501 were Indonesian, with three South Koreans and one person each from Singapore, Malaysia, Britain and France.

The Airbus A320, which took off Sunday morning from Surabaya in Indonesia's East Java province, was about halfway to Singapore when it vanished from radar. The jet had been airborne for about 42 minutes.

A total of 155 passengers and seven crew members were on board, including 16 children and an infant.

The captain in command had a total of 6,100 flying hours and the co-pilot a total of 2,275 flying hours, according to AirAsia. The plane had undergone its last scheduled maintenance on Nov.16, it added.

The incident came at the end of a disastrous year for the Malaysian aviation. Malaysia Airlines Flight MH370, a Boeing 777 with 239 people on board, disappeared on March 8 after diverting from its Kuala Lumpur-Beijing course. No traces of the jetliner have been found despite massive search efforts.

Months later, MH17, also a Boeing 777, went down on July 17 in the war-torn eastern Ukraine en route from Amsterdam to Kuala Lumpur, killing all 298 aboard.

AirAsia, a low-cost carrier, has dominated cheap traveling in the region for years with about 100 destinations and affiliate companies in several Asian countries.