Every day throughout the world, more than eight million people board planes to fly to their destinations.

In the 21st century, air travel is one of the safest forms of transportation thanks to the sophistication of aircraft, the professionalism of Air Traffic Controllers, and strict monitoring by safety regulators.

Furthermore, Malaysia Airlines had a strong safety record, and an enviable reputation within the airline industry as a world class premium carrier.

On board the Boeing 777 was the usual mix of travellers - business people, holiday makers, lovers, relatives looking forward to family reunions. The plane took off without incident at 12.41am local time.

Less than an hour later, the aircraft had lost contact with Air Traffic Control and disappeared from standard radars.

Military radars showed the plane had in fact diverted from its planned flight path back over the Malay Peninsula.

Its last confirmed position before going out of radar range was 370km north-west of Penang, in north-western Malaysia.

Exactly what was occurring on board at that time remains unknown.

Incredibly in an age of sophisticated technology, where satellite dishes can reportedly spot a cricket ball in a desert, there are more questions than answers about MH370’s fate.

Hard facts about the aircraft’s disappearance are so few they barely fill a page.

We know the Malaysia Airlines’ flight from Kuala Lumpur to Beijing took off at 12.41am local time.

We know the weather conditions were good, and the pilot and copilot were well respected with 40-years’ flying experience between them.

We know that the first 38-minutes of the flight were unremarkable, at least as far as those on the ground were concerned.

We know that after the aircraft’s final transmission to Kuala Lumpur Air Traffic Control — “Goodnight Malaysian three-seven-zero” — the Boeing 777 was never heard from again other than a series of satellite pings.

Beyond that, piecing together the fate of MH370 has been an exercise bogged down in confusion and contradictions, wild speculation and for the next-of-kin, enormous grief and frustration.

For the first week after the flight’s disappearance it was thought the plane had crashed into the South China Sea or Gulf of Thailand.

It took the release of military radar data followed by satellite information for the search focus to shift to a remote stretch of the southern Indian Ocean.

After extensive air searches and a costly and ongoing underwater search, nothing of the Boeing 777 had been found - until an aircraft component called a flaperon washed up on a beach on the island of Reunion in the Indian ocean and overnight tests revealed it came from the missing plane.

Detailed drift modelling forecast wreckage would start washing up on the shores of western Indonesia - thousands of kilometres from Reunion late last year. Nothing appeared, until the extraordinary finding on the Reunion coastline last week.

Since then, more modelling has suggested that the finding is consistent with currents in the Indian Ocean but the flaperon is just one component of a massive aircraft.

The question of the absent wreckage is just one of many facing searchers who are the first to point out they are working with estimates and probabilities — not certainties in relation to the missing aircraft.

To put the size of the challenge into context, the Australian Transport Safety Bureau’s Chief Commissioner Martin Dolan points out that in the 2009 case of Air France Flight 447 they knew where the A330 crashed in the Atlantic Ocean but it still took two years to find it.

The search exercise has not been cheap.

Australia’s government allocated $89.9 million towards the search, being jointly funded by Malaysia’s government.

There are still many questions around MH370.

First and foremost — why did the plane divert so dramatically from its path in the first place?

Was it in some strife?

Was it a deliberate act by the pilot or first officer?

Was it under control by someone other than the pilots?

They are not the only questions that have gone unanswered since it disappeared.

Why didn’t Malaysia send up fighter jets to escort the plane — when it stopped communicating with ATC and diverted from its course?

Why did it take four-hours for the plane’s disappearance to be referred by Air Traffic Control to Malaysian search and rescue authorities?

And the most confounding — how could an aircraft as sophisticated as a Boeing 777-200ER carrying 239 people simply disappear without a trace?

So baffling is the mystery of MH370, no-one has been able to come up with an explanation considered plausible.

A detailed theory centring on pilot Zaharie Ahmad Shah as masterminding a dastardly murder-suicide plot was dismissed as fanciful and full of holes.

Had he managed to lock out his copilot and depressurise the cabin without being challenged by flight crew, why were no attempts made to send text messages, if other aircraft communications were cut?

Australian aviation expert Neil Hansford said the flaperon snapping off gave pointers on how the jet entered the water.

“What it does show is that the aircraft has gone into the water in a controlled-type crash and as the engines have hit the water, they’ve sheared off and this part is straight behind one of the engines,” he told AFP.

“There should be at least one other flaperon from the other wing (floating around).”

Other theories — such as hijacking, on board fire, mechanical malfunction, missile strike, cabin depressurisation and sabotage have also failed to satisfy.

US aviation safety expert Captain John Cox is not one to subscribe to crazy theories.

But he does believe the aircraft’s disappearance was no accident — rather a deliberate act by someone on board the plane.

“MH370 is already one of aviation’s great mysteries,” says Captain Cox.

“Never in history has a jet airliner with passengers provided so few clues after so long.

“Until MH370 every jet airliner with passengers aboard has been located and the cause of the accident determined.”

He has reached his own theory based on the very limited evidence available, and his extensive knowledge of aircraft operations.

“We can deduce that someone with specific knowledge interacted with two complex computer systems on the aeroplane — Flight Management Computer and ACARS,” says the captain.

“This level and specificity of knowledge is not common and significantly limits the potential candidates.

“We can deduce that this was a deliberate act based on the precise track along the airspace border of Malaysia,” he says referring to the aircraft’s path across the Strait of Malacca after going off course.

“We can deduce that no outside influence caused the course change, transponder secession or ACARS data termination as there has never been such a case in the history of aviation.

“Therefore the commands were internal.”

Encouragingly, he does believe the mystery will be solved because “we know where the aeroplane isn’t”.

Boeing declined requests for an interview, citing the aircraft manufacturer’s involvement in the official investigation into MH370’s disappearance.

A spokesman told News Corp, Boeing had “provided technical input, such as how far the aircraft could have flown at that weight and amount of fuel”.

“This accident is exceptional in a number of ways — not the least that nothing from the flight has been sighted. Not even a seat cushion,” said the spokesman.

In many ways the mystery surrounding the flight has overshadowed the human tragedy of MH370, which in terms of loss of life, is in the top 20 worst air crashes in history.

Rodney and Mary Burrows were among the six Australians on board. They were travelling with their long-time Brisbane friends, Bob and Cathy Lawton. Both couples have three adult children, and the Burrows were looking forward to becoming first-time grandparents — to daughter Karla’s son, born a month after the flight’s disappearance.

Sydney couple Naijun Gu, 31 and Yuan Li, 33, were thought to be on their way to see their young children in Beijing.

The Malaysian husband of Melbourne’s Jennifer Chong was on a business trip to Beijing, as she made preparations to move into their new home in the up-market suburb of Kew.