The investigators’ last word on the greatest mystery in aviation history appears on page 443 of the MH370 Safety Investigation Report: “The Team is unable to determine the real cause for the disappearance of MH370.”

But they have covered every aspect from the credit-card records of the captain to the species of barnacles found on the aircraft’s flaperon when it washed up on a beach on the island of Reunion.

The 19-strong Malaysian investigation team was supported by national organisations, including the UK Air Accidents Investigation Branch and the Australian Transport Safety Bureau.

The final report is dedicated to “the memory of the 239 passengers and crew missing on MH370”. For their families, friends and colleagues, it at least fills in some of the blanks and rules out some of the speculation about the loss. And for the travelling public, the report makes some intriguing revelations.

What happened to flight MH370?

The Malaysia Airlines (MAS) Boeing 777 was on a routine flight from Kuala Lumpur International Airport (KLIA) to Beijing on 8 March 2014 with 227 passengers and 12 crew on board, commanded by Zaharie Ahmad Shah, a highly experienced captain. The first officer was Fariq Abdul Hamid, who was on his first Boeing 777 mission without a training captain overseeing him.

At 1.19am, the captain acknowledged an instruction from Malaysian air-traffic controllers with the words: “Good night Malaysian Three Seven Zero.” This was the last recorded radio transmission from MH370. “He did not read back the assigned frequency, which was inconsistent with radio-telephony procedures,” notes the report.

During the handover from Malaysian to Vietnamese air-traffic controllers, the aircraft disappeared.

Analysis of radar and satellite data shows that it suddenly changed course, flew back across peninsula Malaysia, turning south of Penang to the northwest and then towards the southern Indian Ocean.

The plane ultimately ran out of fuel and crashed in the Indian Ocean west of Australia, thousands of miles from its intended destination.

“There is insufficient information to determine if the aircraft broke up in the air or during impact with the ocean,” says the report.

What do we know about the plane’s turn off course?

“The turn would have been carried out with the autopilot disengaged, as it was not possible to achieve a turn time of 2 minutes and 10 seconds (as suggested by recorded data) using autopilot,” says the report.

Why did it ‘disappear’ from radar screens?

The transponder stopped transmitting, “whether with intent or otherwise”.

“Although it cannot be conclusively ruled out that an aircraft or system malfunction was a cause, based on the limited evidence available, it is more likely that the loss of communication prior to the diversion is due to the systems being manually turned off or power interrupted to them.”

MH370 debris - in pictures Show all 7 1 /7 MH370 debris - in pictures MH370 debris - in pictures MH370 debris French police officers carry a piece of debris from a plane in Saint-Andre, Reunion Island. AP MH370 debris - in pictures MH370 debris Police carry a piece of debris from an unidentified aircraft found in the coastal area of Saint-Andre de la Reunion, in the east of the French Indian Ocean island of La Reunion AFP PHOTO / YANNICK PITOUYANNICK PITOU/AFP/Getty Images MH370 debris - in pictures MH370 debris The plane part is being taken to France for further investigation Reuters MH370 debris - in pictures MH370 debris French gendarmes and police inspect a large piece of plane debris which was found on the beach in Saint-Andre, on the French Indian Ocean island of La Reunion Reuters MH370 debris - in pictures MH370 debris French gendarmes and police inspect a large piece of plane debris which was found on the beach in Saint-Andre, on the French Indian Ocean island of La Reunion Reuters MH370 debris - in pictures MH370 debris Johnny Begue, a member of a local shore cleaning association, in Saint-Andre, French Indian Ocean island of La Reunion, holds the remain of a suitcase found the day before on the same site Getty Images MH370 debris - in pictures MH370 debris Searches continued on Friday for other possible MH370 debris along beaches on the island of Réunion AP

“It was found that it was difficult to maintain successful call connectivity above 8,000ft. However, one brand of phone was able to make a call at 20,000ft.”

How was the disappearance handled?

Extremely badly, at first. The report catalogues shortcomings and mistakes by air traffic controllers and staff in the airline duty office.

Vietnamese air-traffic controllers failed to question the disappearance for 12 minutes. Had the report been made earlier, ground stations and other aircraft could have begun the search for the missing plane while there was still time to track it.

Staff in the Malaysia Airlines Operation Control Centre reported variously that MH370 was over Cambodian or Vietnamese airspace, neither of which was correct. The false assertions led to early suggestions that the Boeing had landed in Cambodia, raising hopes among relatives of the passengers and crew that they were safe – only to be later dashed.

Again, time was wasted in following up these mistaken statements.

Military air-traffic controllers saw the aircraft way out of position, but did nothing “since it was ‘friendly’ and did not pose any threat to national airspace security, integrity and sovereignty”.

There was a long delay before the first “DETRESFA” message, indicating: “There is a reasonable certainty that an aircraft and its occupants are threatened by grave and imminent danger and require immediate assistance.”

Did technical issues cause the disappearance?

Investigators do not rule out a mechanical problem, but consider it highly unlikely: “There is no evidence to suggest that a malfunction had caused the aircraft to divert from its filed flight plan route.

“The aircraft’s maintenance history and events prior to the last flight do not show any issues that could have contributed and resulted in the deviation and subsequent changes in the flight path.

“The analysis of the relevant aircraft systems taking into account the route followed by the aircraft and the height at which it flew, constrained by its performance and range capability, does not suggest a mechanical problem with the aircraft.

“The investigation is unable to determine any plausible aircraft or systems failure mode that would lead to the observed systems deactivation, diversion from the filed flight plan route and the subsequent flight path taken by the aircraft.”

Is it likely someone was at the controls?

Yes, but it is not clear who. Captain Shah was the last person to be heard by air-traffic controllers.

The report notes: “At the time of flight MH370, there were no requirements for an additional crew member in the cockpit in the event when one of two pilots were to leave the cockpit.

"However, in response to flight MH370, MAS has, since introduced this requirement into its safety procedures effective 27 March 2014, a procedure subsequently introduced by other airlines following the GermanWings Flight 9525 accident on 24 March 2015.”

In a very significant phrase, the investigators say: “The Team does not exclude the possibility of intervention by a third party.

“It could not be established whether the aircraft was flown by anyone other than the pilots”.

If not the pilots, who could have flown the plane off course?

A passenger, or a member of cabin crew. The report does not countenance the possibility that there was one or more other people on board besides those on the manifest.

What was the state of mind of the captain and first officer?

On the captain, the report says: “There was no known history of apathy, anxiety, or irritability. There were no significant changes in his lifestyle, interpersonal conflict or family stresses. Similarly, the FO’s ability and professional approach to work was reported to be good.

“There is no evidence to suggest that the PIC [pilot in command, ie captain] and FO [first office] experienced recent changes or difficulties in personal relationships or that there were any conflicts or problems between them.

Potential passenger belongings from MH370 Show all 13 1 /13 Potential passenger belongings from MH370 Potential passenger belongings from MH370 A bag and pen Blaine Gibson Potential passenger belongings from MH370 The sole of a shoe Blaine Gibson Potential passenger belongings from MH370 A satchel with pen Blaine Gibson Potential passenger belongings from MH370 The inside of a bag Blaine Gibson Potential passenger belongings from MH370 A shoulder bag Blaine Gibson Potential passenger belongings from MH370 The word Mensa, from the high-IQ organisation, on an item Blaine Gibson Potential passenger belongings from MH370 A phone case and pen Blaine Gibson Potential passenger belongings from MH370 A wash bag Blaine Gibson Potential passenger belongings from MH370 A backpack Blaine Gibson Potential passenger belongings from MH370 A camera case Blaine Gibson Potential passenger belongings from MH370 A prayer hat Blaine Gibson Potential passenger belongings from MH370 The sole of a shoe Blaine Gibson Potential passenger belongings from MH370 A luggage bag and pen Blaine Gibson

“There had been no financial stress or impending insolvency, recent or additional insurance coverage purchased or recent behavioural changes for the crew. The radio-telephony communications ... conformed to the routine procedure and no evidence of anxiety or stress was detected in the communications.”

On reports of the captain’s health, the report says: “Scrutiny of his credit card transactions failed to reveal a pattern of regular purchase of over-the-counter medication of any significance, either in local or overseas pharmacies.”

What about reports that the captain practised manoeuvres on a flight simulator at home?

Simulator equipment was taken from Captain Shah’s home shortly after the disappearance, and analysed.

“There were seven ‘manually programmed’ waypoint coordinates, that when connected together, will create a flight path from KLIA to an area south of the Indian Ocean through the Andaman Sea.” But a forensic report concluded “there were no unusual activities other than game-related flight simulations”.

Could the plane have been flown remotely?

No. In 2003, Boeing took out a “Patent on Remote Control Take-over of Aircraft”, designed to foil hijack attempts. “The ‘uninterruptible’ autopilot envisioned by the patent could be activated, either by pilots, on-board sensors or remotely via radio or satellite links by the airline or government agencies if there were attempts to forcibly gain control of the cockpit.

“This system once activated would disallow pilot inputs and prevent anyone on-board from interrupting the automatic takeover. Thus, the personnel on-board could not be forced into carrying out the demands of any unauthorised person(s).”

But the aircraft maker told investigators: “Boeing has confirmed that it has not implemented the patented system or any other technology to remotely pilot a commercial aircraft and is not aware of any Boeing commercial aircraft that has incorporated such technology.”

The report concludes; “There is no evidence to support the belief that control of the aircraft 9M-MRO (operating as MH370) could have been or was taken over remotely as the technology was not implemented on commercial aircraft.”

Could it have been a terror attack?

The word “terror” is not even mentioned in the report, but it notes “no traces of explosion were found” on two pieces of debris that are almost certainly from the cabin interior.

What about the suggestion of a cargo fire?

This theory is based on the fact that mangosteen fruits and lithium batteries were stored in the same cargo compartment, and “could have got into contact with the batteries and produced hazardous fumes or in a worst case scenario caused a short circuit and/or fire”.

But tests showed “the two items tested could not be the cause in the disappearance of MH370”.

Is there any other information in the report?

Yes. The report reveals that the first officer’s mobile phone was in contact with a ground station on the island of Penang. “The signal ‘hit’ however did not record any communication except to confirm that it was in the ‘on’ mode.” A plane was sent up to 24,000 feet to see how mobile phones perform at altitude.

One cabin crew member was missing. “To efficiently carry out the duties that include in-flight customer services including serving passenger meals, MAS had established the need to carry 11 cabin crew members.

“MH370 however departed with only 10 cabin crew members, 1 less than the normal compliment. MAS was then facing acute shortage of cabin crew resulting in flights departing with under-strength crew complements from the numbers normally required on many of their aircraft operations in the past year.”

The investigators do not ascribe particular significance to either of these aspects.

What recommendations does the report make?

Mainly about keeping track of planes: “The disappearance of MH370 and the search effort are unprecedented in commercial aviation history. Improvements must be undertaken to ensure that this type of event is identified as soon as possible, and mechanisms are in place to track an aircraft that is not following its filed flight plan for any reason.

“In this technological epoch, the international aviation community needs to provide assurance to the travelling public that the location of current-generation commercial aircraft is always known. It is unacceptable to do otherwise.”

Will we ever find out what happened?

Two extensive underwater searches have failed to find any trace of MH370. It may be that advances in underwater drone technology allow a much lower-cost, larger-scale search of the sea floor to be carried out.

“This Report will necessarily be limited by a significant lack of evidence,” concede the investigators, pointing out: “The aircraft’s Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR) have not yet been located.”

The aircraft was equipped with two crash-protected recorders, both of which are designed to be protected against immersion in sea water to a depth of 20,000 feet. In the case of Air France flight 447, which crashed in the Atlantic, the recorders were invaluable in piecing together events that led to the tragedy.

The FDR records 1,300 parameters from the most recent 25 hours of flight; it could reveal the controls that were commanded during the final flight of the Boeing 777. The CVR records sounds on the flight deck, but may be limited to the last two hours of the flight, rather than containing evidence of what happened when the fateful first turn was made.