中国加入亚航失踪飞机搜索工作

The Chinese navy and air force are joining the search and rescue effort for the missing AirAsia plane.

The Chinese Defense Ministry says a frigate on routine patrol in the South China Sea is heading for the waters where the plane went missing.

An Air Force jet is also making preparations and coordinating with the countries on the flight route.

Indonesia is leading the search effort while Singapore, Malaysia, and Australia have contributed planes.

Earlier, the head of Indonesia's search-and-rescue agency said the missing jet with 162 people on board is believed to have sunk to the bottom of the sea.

Bambang Soelistyo said the hypothesis was based on the co-ordinates of the plane when contact with it was lost.

Indonesian Vice President Jusuf Kalla has vowed that his country will continue the search.

"There are 30 ship operation in the area and around 15 airplane and helicopters operating there. It is not easy of course in the operation in the sea, especially in the bad weather like this, but the President's instruction to all our people to do the best, and fast and (there is) no limit to find the plane and the passengers."

Search teams are still attempting to gain a signal from the airplane's Emergency Locator Transmitter.

The device is supposed to become active in the event of a crash.

Professor Huang Jun with Beijing-based Beihang University says there are reasons why a plane's emergency locator might not activate.

"First, the signal could be out of the reach of the search vessels. There are limits to how far the signal can transmit. The second possibility is that the signal is blocked by other objects. The other possibility is that the power to the transmitter is off."

On Monday, broad aerial surveys spotted two oily patches and objects in separate locations, but it's unknown whether any of it is related to the missing Airbus.

Authorities say the search area will be widened on Tuesday.

Most of the passengers on board were Indonesian.

Hong Kong authorities have confirmed that a resident of the city was onboard with his two-year-old daughter.