Flight MH370: four unanswered questions

Who was flying the plane when it disappeared?

Aviation experts have suggested the disabling of communications systems and the navigation of the plane imply it was piloted by someone with considerable flying experience and technical knowledge – inevitably focusing attention on the captain and first officer.

Suspicions are further raised by the news that the last words from the cockpit – “All right, goodnight” – were made after one of the communications systems was turned off.

But Malaysian officials have not indicated which of the pilots was speaking. In fact, they may not know if it was one of the pilots at all . "It's a radio communication and can distort voices. You are talking to so many aeroplanes and pilots that you wouldn't know who that was [on the other end]," said Paul Drechsel, an air traffic control specialist at the University of North Dakota.

Air traffic control voice communications are routinely recorded in the US, he added. But even if that is the case in Malaysia, it is unclear how much a recording can reveal.

Malaysia’s transport minister said yesterday that the two men had not asked to fly together, suggesting that even if one of them had planned the diversion, it is unlikely both had.

The pilot of another flight, who attempted to contact MH370 just after 1.30am at the request of Vietnamese air traffic control authorities who could not reach it, thought he heard the first officer through interference but was not certain.

What do we know about the crew and passengers?

Police announced on Tuesday they were looking at the background of all the crew and passengers – but it was not until this weekend that they searched the homes of the pilot and first officer. Insp GenKhalid Abu Bakar said authorities "didn't see the necessity in the early stages".

He told a press conference that “a few foreign intelligence agencies have cleared all the passengers ”, but went on to say a few countries had yet to reply to the request for background checks. It is not clear how fully the rest of the crew and passengers have been checked; have they simply been screened for links to terrorist or criminal organisations? Have they been vetted for flying experience? Have potential personal problems been explored, as police suggested they would be earlier this week?

Why did no one on board act to intervene?

Some have asked why no one tried to raise the alarm if the plane was flying for so long. Why did passengers not make phone calls as those aboard the hijacked United Flight 93 did in September 2011.

It may be that, at least initially, passengers and crew were unaware anything was wrong. If, for example, one of the pilots incapacitated or forcefully coerced the other, those outside the cockpit might not be aware of the problem.

Another possibility is that passengers and the crew were somehow terrorised into compliance, either through threats or through an accomplice in the cabin. A third theory is that the plane’s apparent climb to an altitude of 45,000 f t early after diversion might have been designed to incapacitate others on board by inducing hypoxia – oxygen deprivation – which quickly causes disorientation and unconsciousness and can lead to death. But the radar readings are not absolutely certain and in any case Boeing-777s are certified to fly at up to 43,000 feet; counting on a cabin depressurisation just 2,000 feet above this seems unlikely.

Oxygen supplies are also kept in the cabin for crew members, in addition to the oxygen masks. In all, it would be an elaborate plan with limited prospects of success.

Finally, it is possible that more than one explanation is relevant. If whoever diverted the plane had set a new flight path, the plane could have continued to fly for hours even if that person was incapacitated for some reason – such as hypoxia. Planes have flown for thousands of miles with unconscious crews.

What will we learn from the cockpit voice recorders?

The problem is that the plane and its “black box” flight data and voice recorders have to be found first. If the plane has crashed into the southern Indian Ocean, as some officials have indicated they fear is likely, searchers face a huge expanse of ocean with powerful currents much of which is not covered by radar, so tracking the aircraft’s last known movements could be very tough.

Even if the approximate location is known, the strength of the signals from the recorders’ electronic beacons can be affected by the depth of water and whether they are trapped underneath wreckage. They only transmit for a bout 30 days – meaning time is limited.

– ( Guardian service)