A week after Indonesia AirAsia QZ8501 crashed into the Java Sea presumably killing all 162 people on board, search teams are expected to intensify the hunt for the still missing aircraft and its black boxes.
Typically painted orange for easy detection, the black boxes, as they are referred to, record conversations in the cockpit and preserve data on aircraft position and speed - which can be crucial in determining the cause of accidents.
With dozens of bodies and some pieces of wreckage already recovered from the Airbus 320-200, which crashed enroute from Surabaya to Singapore, air crash experts expect the main body of the plane and the aircraft recorders to be found within the week or so.
When SilkAir MI185 crashed into the Musi River near Palembang, Indonesia, in December 1997, it took nine days to find the black boxes. A decade later, when a plane belonging to the now- defunct Indonesian carrier Adam Air crashed at sea off Sulawesi Island, the recorders were recovered after three weeks.
An Indonesia-led, multi-nation search based in Pangkalan Bun, a town in southern Borneo closest to the QZ8501 search area, is currently concentrating on about 1,350 square nautical miles of the northern Java Sea.
It would have been still dark when Captain Iriyanto and his French co-pilot Remi Emmanual Plesel, along with the flight's four cabin crew and one engineer, arrived at Surabaya's Juanda Airport.
Weather charts issued before the flight showed that the plane's scheduled route at cruising level would come across "worrying" conditions, Indonesia's weather officials said in a report last Friday.
Satellite images also suggested temperatures of minus 80 deg C to minus 85 deg C, which meant there were grains of ice in the dense clouds.
It is unclear if the information was conveyed to the pilots.
At 5.30am, QZ8501 took off with 23 no-shows, including a family of 10 which missed the flight because they did not get the message from the airline informing them of a change in flight time. They had likely booked their tickets before the end of March, after which the airline brought forward the flight timing from 7.20am to 5.20am local time.
In a bizarre development, Indonesia's Transport Ministry is now saying the airline did not in fact have approval to operate the sector on Sundays, and has suspended services pending checks.
A key question is why air traffic control was unaware of this.
For the 155 passengers on board the flight that Sunday morning - all were Indonesians except for a two-year-old Singaporean girl, a Malaysian, one Briton and three South Koreans - the day had presumably started out uneventfully.
The first hint of trouble came about 45 minutes into the flight, at 6.12am local time, when the cockpit contacted air traffic control for permission to turn left to avoid a storm.
The pilots also asked for approval to climb from 32,000 feet to 38,000 feet, which was denied because there were other aircraft flying higher.
Clearance was given for QZ8501 to climb to 34,000 feet, but when this was conveyed to the cockpit, there was no response.
At 7.55am local time - an hour behind Singapore time - AirAsia declared the plane missing.
And at Changi Airport Terminal 1, where the plane had been scheduled to land at 8.30am, relatives and friends of those on board waited.
Two days after QZ8501 went down, the first bodies and debris were recovered.
Soon after the authorities announced they had most likely found debris from the ill-fated Airbus A-320, group chief executive officer of AirAsia Tony Fernandes took to Twitter to deliver a personal apology.
"My heart is filled with sadness for all the families involved in QZ8501," he wrote. "On behalf of AirAsia my condolences to all. Words cannot express how sorry I am."
From engaging the public and visiting affected families to rallying his staff and accompanying the remains of cabin crew member Khairunnisa Haidar, 22, back to her hometown in Palembang, Mr Fernandes has earned much praise among the public and the online community for his personal touch.
But for grieving relatives and friends at the next-of-kin crisis centre at Juanda International Airport, it was all too much to bear as all hopes faded and they now awaited the arrival of recovered bodies.
Search teams being coordinated from Pangkalan Bun are now combing about 13,500 square nautical miles of the Java Sea, but progress has been hampered by rough seas, with waves reaching a height of 4m.
This has prevented the recovery of two big objects - the larger of which is 10m by 5m - that have been spotted and are believed to be parts of the plane.
More than 90 vessels and aircraft are involved in the operations, involving countries such as Indonesia, Singapore, Australia, South Korea, Japan and the United States.
The Singapore Armed Forces has contributed more than 400 personnel, two C-130 aircraft, two Super Puma helicopters, five navy ships and a six-man Autonomous Underwater Vehicle team.
Why did QZ8501 crash?
The facts will not be established until the black boxes and other critical data are recovered and analysed, but all signs point to severe weather conditions as the likely culprit.
In a 14-page report released last Friday, Indonesia's Meteorology, Climatology and Geophysics Agency said: "The most probable weather phenomenon is that icing caused the plane engines to be damaged."
Leaked radar data, which still needs to be verified, suggests the same.
Before it crashed, the plane had allegedly climbed at a rate of 6,000 feet to 9,000 feet per minute, before falling at a rate of 11,000 feet per minute, with sudden drops of up to 24,000 feet per minute.
Mr Jacques Astre, president of industry consultancy International Aviation Safety, said: "The (climb) rates sound excessive...
"Given the altitude and potential weight of the aircraft, such a rate of climb sounds quite excessive for the aircraft's capability... Could updrafts from a violent thunderstorm propel an aircraft upward at a violent rate? Yes."
A similar incident occurred in June 2009 when Air France Flight AF447 plunged into the Atlantic Ocean during a flight from Rio de Janeiro to Paris.
Investigations concluded that the aircraft crashed after the pilots failed to react correctly to temporary inconsistencies between air speed measurements, likely because ice crystals had blocked the plane's pitot tubes that measure air speed.
While it is unlikely that QZ8501 exploded in mid-air, experts said the impact upon hitting the ocean would have broken the plane up.
Whether those on board died from drowning or from the impact would need to be forensically determined, but either way, they would likely have been knocked out during the steep fall, experts said.
The QZ8501 crash capped a disastrous year for the air travel industry, already buffeted by the disappearance of Malaysia Airlines Flight MH370 in March and the shooting down of Malaysia Airlines Flight MH17 in July.
Flying remains the safest mode of travel - from 90 air accidents in 2009, there were 81 last year. But every major accident exposes gaps that need to be fixed.
The disappearance of MH370 sparked urgent global action for better aircraft tracking and surveillance systems. The shooting down of MH17 over Ukraine showed the need for more effective ways of gathering and disseminating information so airlines are able to assess the risks associated with flying over conflict zones.
The crash of QZ8501 will leave its own mark on the aviation industry.
But for now, all efforts are focused on the search operations as air crash investigators prepare for the arduous task of piecing together the final minutes and seconds of the flight.
This article was first published on January 4, 2015.
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