The Indonesian jet crashed into the sea without issuing a mayday, killing all 102 people on board. Months later its wreckage and in-flight recorders lie on the seabed amid a dispute over who should recover them - a delay that experts say may jeopardize global air safety.
"I find it impossible to believe that we can have, in the 21st Century, an aviation accident with a modern aircraft and no successful attempt to get the recorder," said Jim Hall, former chairman of the U.S. National Transportation Board.
Hall said it is important to learn if the Boeing 737 - the world's most popular airplane - had structural problems.
Other aviation experts agreed, saying time is running out.
"Saltwater is corrosive, so the longer the black boxes are submerged, the greater the damage potential," said Paul Czysz, a professor emeritus at St. Louis University in the U.S. state of Missouri.
"To one outside the event, it would appear that determining the cause of the crash is not in the forefront of activities," he said.
Indonesia has recently seen a string of plane crashes.
Last week, a Boeing 737 careened off a runway, bursting into flames and killing 21 people.
The month before, a jetliner's fuselage split in half on a hard landing, sending carry-on luggage flying through the cabin but causing no injuries.
Indonesia's government has acknowledged it does not have enough quality personnel or technology to match the needs of its booming aviation sector.
This week, the country's top aviation official was fired. Many believe beleaguered Transport Minister Hatta Rajasa may be next.
Signals from the Adam Air flight recorders, often called "black boxes," have been traced to the ocean floor at a depth of about 1,700 meters (about a mile), but the government lacks the technology to salvage them.
Frans Wenas, head of the ministry's safety committee, said it is up to Adam Air to recover the black boxes from the New Year's Day crash - but at such a depth, it would be costly and difficult.
The budget airline said an agreement with U.S-based Phoenix International fell through after the company failed to guarantee recovery. Negotiations with another firm are now under way, said Capt. Hartono, Adam Air's director of safety and security, who goes by only one name.
"I don't see how any responsible salvage company could guarantee recovery," said Czysz, the aviation expert. "The longer the delay in locating the 'black boxes' the less the possibility they will be located."
Crash investigators have said they believe a mid-air explosion was not the likely cause of the accident because little wreckage was found, suggesting the plane had plunged into the water intact at great speed, the AP reports.
Without data from the flight recorders or the recovery of significant pieces of fuselage, experts say that reaching a definitive conclusion on the cause of the accident will be impossible.
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