China Boeing crash: pilot's illness to terror attack, multiple angles probed

Investigation is underway to determine cause of the fatal plane crash in China's Guangxi region with 132 people on board.

Flight MU5735 from Kunming to Guangzhou went down without an emergency radio call from pilots, slamming into a forested hillside about 100 miles from its destination, according to the Civil Aviation Administration of China.

Over the week, rain and bad weather has hampered with search operations at the crash site, but investigating teams have found two black boxes among 183 other parts of the aircraft. The black boxes, which contain flight data as well as the cockpit recorder, have been sent for analysis.

Cockpit recorders which contain the conversations between the pilots, will aid in determining the exact cause of the crash. The hunt for the flight data recorder is still on.

Speculation about the cause of the crash range from equipment malfunction, to a weather-related event, to pilot illness or suicide, to a terrorist attack of some description. Nothing has been ruled out yet.

As investigators work on putting together the puzzle pieces,

here are the different possible causes of the crash that have been propounded so far:

1. Terrorist attack

According to reports, the aircraft did not report any technical snags and aviation authorities have confirmed that there were no weather issues or any other problems. Chinese investigators said air traffic controllers tried to reach pilots of the doomed jet multiple times after it tipped into a dive, but received no response.

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2. Pilots' illness or suicide

The pilots at the control of China Eastern Flight 5735 included one of China's most experienced commercial aviators and a much younger captain with a family pedigree, according to media reports in China. The captain had logged 6,709 hours in the 737 model, while the first co-pilot had a total of 31,769 flying hours, officials said at a briefing. The second co-pilot had 556 hours of flying hours experience. They all had good performance records and stable family conditions.

As per reports, investigating authorities have reason to believe that no communication from the pilots before the plane's steep descent could be because of poor mental health of one or all the pilots.

3. Chinese authorities have not yet declared the official cause

A Bloomberg News review of Flightradar24 data showed the jet was flying well above normal speeds during the dive, possibly nearing the speed of sound. Aircraft such as the 737-800 are designed not to dive so aggressively, so some kind of aircraft failure or pilot action would be required to keep its nose pointed down for so long.

China Eastern said it is carrying out a comprehensive investigation into the crash. A spokesman said the plane was brought into the fleet in June 2015, its maintenance followed a strict plan and its technical condition was normal and stable. The airline grounded all its Boeing 737-800 jets from Tuesday but has since emphasised that the move does not necessarily mean there are any safety issues with that type of aircraft.

China's Vice Premier Liu He has been tasked with overseeing the investigation, which will be carried out by the Civil Aviation Administration of China. Authorities will work alongside a senior investigator from the U.S. National Transportation Safety Board and representatives from Boeing and the U.S. Federal Aviation Administration.

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