By Shashank Bengali and Ahmad Pathoni, Los Angeles Times (TNS)

JAKARTA, Indonesia — The first full day of a growing, multi-nation hunt for an AirAsia passenger jet lost over Indonesian waters ended Monday with few clues to its disappearance and a grim acknowledgment by officials that “the worst may have happened.”

Helicopters and surveillance aircraft from Indonesia, Malaysia, Singapore and Australia returned to their bases, some after flying 10 hours or more over a choppy Java Sea, the focal point of the search for the airliner that was carrying 162 mostly Indonesian passengers.

The first tantalizing possible traces of the missing Airbus A320-200 – which lost contact with air-traffic control during a two-hour flight to Singapore from the Indonesian city of Surabaya on Sunday morning – were inconclusive or ultimately discounted.

Air Force spokesman Hadi Tjahjanto told The Times that searchers in a helicopter and C-130 plane had seen an oil slick about 105 nautical miles off Indonesia’s Belitung island near the Karimata Strait, which connects the archipelago nation to Singapore.

“We’re checking whether it’s jet fuel or fuel from a ship,” he said.

An Australian Orion aircraft spotted “suspicious objects” in the sea near Nangka island, northeast of the Belitung, about 700 miles from where the plane lost contact, prompting teams to rush toward the area under cloudy skies. But Bambang Soelistyo, the head of Indonesia’s National Search and Rescue Agency, which was leading the effort, said the weak signal detected by the Australian plane came from a personal locator beacon, not the missing jet’s emergency transmitter.

Bambang said that based on the coordinates of Indonesia AirAsia Flight 8501’s last known location, investigators believed it had crashed into the Java Sea north of Jakarta.

“My goal is to locate it as soon as possible,” Bambang told a news conference in Jakarta. “We’re doing the best we can.”

Indonesian Vice President Jusuf Kalla said “bad weather” was hampering the search but expressed hope that the plane would be found.

“We don’t set deadlines. What is important is we find the plane and its passengers,” Kalla said.

Asked about the prospects of finding survivors more than 36 hours after the flight went missing, Kalla said: “We pray for them but we realize the worst may have happened.”

Bambang said teams searched an area comprising roughly 66,000 square miles in four sectors on Sunday, concentrating on a 250-mile-wide stretch of the Java Sea between the Indonesian islands of Sumatra and Borneo. On Monday the search expanded to the north to include the Karimata strait and the coasts of Belitung island and West Kalimantan province, he said.

Indonesia’s armed forces had deployed transport helicopters and naval ships while Malaysia and Singapore had each sent C-130 Hercules transport aircraft and three ships to help ferry teams to and from the search site. Early Monday, Australia’s Orion surveillance aircraft joined the effort.

If wreckage isn’t found at the water’s surface, investigators likely would begin scouring the sea floor for the Airbus A330-200 — probably requiring contributions of advanced ships and equipment from other nations.

“If that’s the case, we’ll have difficulty determining the location because our equipment is not adequate,” Bambang said.

Singapore civil aviation officials said they were preparing to send two teams of specialists and underwater locator beacons to help find the missing jet’s flight data recorders.

China offered to send airlines and ships to join the search and rescue efforts, foreign ministry spokeswoman Hua Chunying said in Beijing. South Korea said it would send a surveillance plane later this week, the Yonhap news agency reported.

In Washington, Pentagon officials said Sunday they were ready to assist but had not been asked.

AirAsia executive chief Tony Fernandes defended his airline’s safety record, saying it had carried 220 million passengers in 13 years and never had a fatal accident.

“Until we have a full investigation, we don’t want to speculate,” Fernandes told a news conference in Surabaya. “It’s premature to talk (about what went wrong) at the moment. We are confident in our ability to fly people. We’ll continue to be strong and continue to carry people who never fly before.”

Indonesian transportation ministry Ignasius Jonan said the government would review AirAsia’s operations “to ensure that in the future its activity will be better.” The low-cost carrier, which is based in Malaysia and operates mainly short flights across Southeast Asia, has a strong safety record and is widely regarded as one of the world’s most successful budget airlines.

It was the third air disaster this year involving a Malaysian airline. Malaysia Airlines Flight 370 vanished in March en route to Beijing with 239 people aboard and is still missing, while the same carrier’s Flight 17 was shot down over eastern Ukraine, killing all 298 passengers and crew.

Investigators were hopeful that recovering the flight data recorder would offer clues into the AirAsia plane’s disappearance. The aircraft departed Surabaya roughly on schedule at 5:35 a.m. Sunday but apparently encountered heavy clouds during what is normally the wettest time of the year in Indonesia.

Indonesian transport authorities said the pilot communicated with air-traffic controllers at 6:12 a.m. asking permission to take a left turn off the scheduled flight path and climb from 32,000 feet to 38,000 feet to avoid clouds.

According to multiple reports, the request to raise altitude was denied due to other aircraft in the area. The plane disappeared from radar at 6:18 a.m.

Families of the 155 passengers and seven crew members gathered at Surabaya’s airport and Changi international airport in Singapore where AirAsia and government officials had set up crisis centers. Among those on board were 17 children and one infant, the airline said.

“AirAsia Indonesia’s primary focus remains on the families,” the airline said Monday. AirAsia Indonesia CEO Sunu Widyatmoko was in Surabaya meeting with families while other airline officials were doing the same in Singapore, it said.

A tearful Hartatik Sukorini told Indonesia’s TVOne news channel that her daughter Dona was on the plane and said she was hoping for “a miracle.”

“I pray to Allah that she is safe and protected,” she said. “She is a good daughter and never causes me any trouble.”

AFP Photo/ Juni Kriswanto