Now the flight data recorders from Air Asia flight QZ8501 have been found investigators have a chance to find out what really brought down the aircraft with 162 passengers and crew on board.

Divers have recovered the flight data recorder which records around 2,000 parameters from the aircraft systems, such as airspeed, altitude, heading, flight control positions, engine data and many more. They are also reported to have located and recovered the cockpit voice recorder which records the last two hours of voice communications and, via a cockpit area microphone, other noises in the cockpit.

The discovery and recovery of these black boxes marks the first major breakthrough in the search effort since the flight QZ8501 disappeared on December 28, 2014, en route from Surabaya in Indonesia to Singapore.

Questions with no answers

Since the initial disappearance there has been much speculation as to what happened to the flight. The last known communication between air traffic controllers and the pilots was their request to climb to avoid some bad weather which was denied by air traffic controllers. Soon after the aircraft disappeared.

Air Asia said earlier this week that 48 bodies have so far been recovered from the Java Sea with 34 identified. Wreckage from the Airbus A320-200 is also still being recovered.

Investigators will be keenly interested in what the flight data recorder and cockpit voice recorder will reveal. Their recovery was vital.

Until now the available information coming from the investigation supported many diverse scenarios which could have led to the loss of the aircraft, passengers and crew. Some theories were more plausible than others but none were supported by conclusive facts.

The data analysis begins

If the recorders are undamaged, it should only take a few days or even less for the data to be downloaded from the recorders and analysed.

Sophisticated computer modelling programs can use the recorded data to provide real time computer generated video images of what took place. This will show in detail all the progress of the final stages of the flight, readings of all the relevant flight instrumentation, flight control movements, all synthesised with what was said on the flight deck. Investigators will get a very clear picture of what took place.

Analysis of the wreckage as it’s recovered from the sea floor may also help shed light on what happened. The distribution of the wreckage may give an indication of whether there was any inflight break up, separation of any flight critical components or whether the aircraft entered the water intact. Analysis of any structural failures and other damage will also help provide evidence of what happened.

Of course, the investigation will then need to focus on looking for evidence of why whatever happened, happened. But this may not be as easy as it sounds.

Let’s assume that the aircraft entered icing conditions – as has been speculated – and ice formation adversely affected the air pressure detection capability of the pitot heads, used to measure air speed.

If that were the case, the ice will have melted long before the investigators have an opportunity to inspect the systems recovered from the wreckage. So, investigators will have to carefully analyse the flight recorder data looking for deviations in those critical systems which are fed with signals from the pitot heads which may be consistent with what could be expected if icing of the pitot heads had occurred. Icing may also become more of a focus if no other malfunctions or contradictory evidence is found.

Of course this is just one of many possible causation scenarios which the already available information supports. Forensic analysis of all evidence available to the investigators may reveal something different entirely.

Questions of passenger flight safety?

The crash of Air Asia flight QZ8501 comes after a difficult year for the passenger airline industry.

The search is still on going for the missing Malaysia flight MH370. That aircraft departed Kuala Lumpur in Malyasia on March 8, 2014, and was en route to Beijing,but the search effort is now concentrated in deep water off the coast of Western Australia.

How the Malaysia Airlines' Boeing 777 with 239 passengers and crew on board may have gone down there is still a mystery.

Then on July 17, 2014, there was the downing of Malaysia Airlines flight MH17 which had not long before left Amsterdam airport with 283 passengers and 15 crew on board, heading for Kualar Lumpur airport in Malaysia. Evidence from the wreckage suggests the Boeing 777 was brought down by a missile as it flew over troubled areas in the Ukraine.

So the crash of another aircraft is only going to raise concerns over passenger airline safety. But how unusual is the flight QZ8501 case?

The safest part of flying

Ordinarily, airliner accidents during the cruise stages of flights are the most infrequent, as the the Boeing Statistical Summary of Commercial Jet Airplane Accidents 1959 to 2013, published in August 2014 shows.

Note that only 10% fatalities occur during the main cruise period of flights from 2004 through to 2013.Boeing's Statistical Summary of Commercial Jet Airplane Accidents, Worldwide Operations 1959 -- 2013.

So the recent spate of mid flight crashes, if you take MH17 and MH370 into consideration (even though they may both yet be confirmed to be due to acts of terrorism, they still represent failures of the overall aviation safety arrangements), is really atypical of the experience of the past ten years where only one in ten accidents have occurred mid flight.

The Boeing report also shows that 57% of the average flight time is in the cruise phase of flight – where only 10% of fatal accidents have occurred – against 16% of time for take-off and climb (22% of accidents), 26% of time on descent and approach (33% of accidents) and significantly 1% of time on landings (25% of accidents) which is clearly the highest risk time.

Despite these high profile accidents, 2014 had the least number of fatal accidents in the previous ten years although the number of actual casualties was high.

Over that same ten year period, the number of flights flown annually by the worlds airlines has steadily grown.

Airlines globally can statistically be shown as providing the safest form of transport of all. That enviable record has been won by ensuring that the lessons are systematically learned from those accidents which do occur.

Accordingly, it is vital that the industry learns everything it can from QZ8501, MH370 and MH17 to inform future improvements in the aviation safety system.

Geoffrey Dell does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.