An AirAsia sign is pictured at its check-in counter at Changi Airport in Singapore
An AirAsia sign is pictured at its check-in counter at Changi Airport in SingaporeReuters

Indonesia has requested help from the United States to search for a missing AirAsia jetliner, officials in Washington said Monday, according to the AFP news agency.

The State Department also confirmed that no Americans were on Flight QZ8501, which disappeared on Sunday over the Java Sea with 162 people on board.

"Our embassy in Jakarta is in close contact with Indonesian officials, and today, we received a request for assistance locating the airplane," said State Department spokesman Jeffrey Rathke.

"We are reviewing that request to find out how best we can meet Indonesia's request for assistance," he added.

Rathke noted it would take "a little bit of time" to evaluate the request, without detailing what kind of aid -- military or otherwise -- the United States might provide.

Pentagon spokesman Rear Admiral John Kirby said the aid could include "some air, surface and sub-surface detection capabilities."

"We stand ready to assist in any way possible," he added, according to AFP.

Indonesia's top rescue official said on Monday morning that authorities believe the missing AirAsia jet is likely at the bottom of the sea, based on radar data from the plane's last contact.

"(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 in the bottom of the sea," said Marsdya Tni Hendry Bambang, head of Indonesia's national search and rescue agency.

Indonesia resumed at dawn Monday the search for the plane, with assistance from Australia, Malaysia and Singapore.

Australia is already leading the search for another missing aircraft, Malaysia Airlines Flight MH370, which disappeared in March with 239 people on board and is believed to have crashed in the remote Indian Ocean far off Australia's west coast.

No sign of that plane has so far been found and a range of theories as its fate have emerged – from hijacking to crashing to being diverted for use in a terror attack, possibly against Israel. Later theories have become even wilder, ranging from an onboard fire to a suicide mission