US, China join expanding hunt for AirAsia jet

The U.S. joined the growing international effort to locate missing AirAsia flight QZ8501 as search operations entered their third day on Tuesday.

The USS Sampson, a destroyer, is scheduled to reach the search area in the Java Sea later on Tuesday, according to the U.S. Navy, helping to broaden the scope of the search.

Also, China late Monday said it would dispatch a naval ship and air force jet alongside Singapore, Malaysia and Australia, which have already deployed assets to assist in the Indonesia-led search involving some 30 ships and 15 aircraft.

With more ships and planes, the search area will also be expanded to include islands in the area as well as land on Indonesia's side of Borneo, Reuters reported.

Oil test results awaited

Monday's search efforts yielded some conflicting leads reminiscent of the aftermath of MH370's disappearance, which saw several false leads.

An Indonesian helicopter reported two oil slicks within the search area and an Australian surveillance aircraft spotted objects elsewhere in the Java Sea.

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Indonesian authorities later confirmed the debris was not from the aircraft and said that oil samples would be collected and analyzed, with results expected on Tuesday.

The flight carrying 162 people—including 155 passengers, two pilots, one engineer and four cabin crew—to Singapore from Surabaya, Indonesia went missing early Sunday.

Read MoreAirAsia: shallow seas don't mean an easy search

Indonesia's National Search and Rescue Agency told reporters at a press conference on Monday that the plane was likely at the bottom of the Java Sea.

"Our evaluation of the coordinates that we have received suggested that it is under water, so our presumption now is that the aircraft is under the sea," Bambang Soelistyo, head of Indonesia's National Search and Rescue Agency, said.

Challenging weather

The search for the plane has proved challenging amid difficult weather conditions – including heavy rains and thunderstorms – which are suspected to have played a role in the flight's sudden disappearance.

The Airbus A320-200, which departed Surabaya around 5:35 a.m. local time on Sunday (5:30 p.m. ET Saturday), lost contact with air traffic control about 42 minutes after takeoff.

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The aircraft had requested to change course due to weather en route, but permission was declined due to traffic in the area. By the time it had been given clearance, just four minutes after its last correspondence, the jet had disappeared from radar, Bambang Tjahjono, director of the state-owned company in charge of air traffic control, told The Associated Press. No distress signal was sent.

Air Asia's fleet of short-haul planes had been undergoing an upgrade to make them easier to track; however, QZ8501 had not yet been modified, according to a Dow Jones report.