JAKARTA (AFP) - Caught in stormy weather, the pilot of AirAsia flight QZ8501 requested to climb to a higher altitude but was not immediately granted permission due to heavy traffic. Soon afterwards, the jet disappeared off the radar.
While the causes of last month's crash in Indonesia are still being probed, experts say the final moments before the accident point to the perils of flying in a region where safety standards are struggling to keep pace with crowded skies.
South-east Asia's aviation sector has enjoyed some of the fastest growth rates in the world in recent years, with Indonesian airlines in particular expanding rapidly, due to strong economies and an emerging middle class. While observers believe most airlines have made progress in safety, they say the lack of well-trained personnel and decent infrastructure to cope with the increasing number of jets is a concern.
Mr Shukor Yusof, founder of Malaysia-based aviation research firm Endau Analytics, said that Malaysia and Singapore had kept up, but others - in particular Indonesia - had not. "They (Indonesia) really must spend more time and effort to develop capacities to handle this," he said, adding that areas including training, infrastructure and safety all needed attention.
Some analysts worry about the capacity of air traffic control systems to cope, although there is no indication as yet this caused the crash of the AirAsia jet, which went down on Dec 28 en route from Indonesia's Surabaya to Singapore. A total of 162 people were on board when the Airbus A320-200 crashed into the sea. Fifty-one bodies have so far been recovered, as well as the plane's black boxes, and divers are trying to reach the main wreckage in the hope of finding more.
"The real question is the professionalism of the air traffic controllers," said Mr Greg Waldron, Asia managing editor for industry publication Flightglobal.
Pressure on air traffic control was found to have contributed to the May 2012 crash of a Russian Sukhoi passenger plane into a mountain on Indonesia's main island of Java, which killed all 45 people on board.
Although much blame was laid on the pilot for ignoring alerts from the plane's warning system, the one overworked controller on duty in Jakarta was trying to communicate with 14 aircraft at the same time, according to a report from crash investigators.
Inadequate radar systems also failed to warn the plane that it was flying too low, as they should have done.
Others expressed concern about a lax safety culture, pointing to an air traffic control incident in Vietnam last year. Two planes almost collided at an airport in Danang when a young intern was left in charge of directing a busy runway.
Another worry is a lack of trained pilots as airlines rapidly expand - Indonesian budget carrier Lion Air has in recent years made two of the world's largest plane orders, worth US$46 billion (S$61 billion).
Each plane needs five to six pilots, said Mr Waldron, describing the situation as a "real challenge".
The pilot of flight QZ8501 was highly experienced and used to fly military jets, but a lack of training has been blamed for other accidents.
This was the case when a Lion Air jet with a rookie pilot at the controls undershot the runway and crashed into the sea in Bali last year. The plane split in two, but all 108 passengers and crew survived.
Observers say it is not just better pilots and air traffic controllers that are needed, but more experienced personnel across the whole industry, from maintenance workers to safety inspectors.
Despite the concerns, experts stress that Indonesia has actually improved its safety record greatly in recent years following a string of fatal crashes.
All Indonesian carriers were banned by the European Union in 2007 but now a small number, including flag carrier Garuda and the Indonesian branch of Malaysia-based AirAsia, can fly to Europe.
And most analysts reject the notion that governments should seek to put curbs on the industry's growth, saying countries should focus on improving oversight.
"You can't really stop the growth," said Mr Gerry Soejatman, a Jakarta-based independent aviation analyst. "It is fed by the economy and it feeds the economy."