Why did it take so long before anyone realised the plane was missing?



It didn't. Malaysia's acting transport minister, Hishammuddin Hussein, has confirmed that the plane ceased communicating with ground control about 40 minutes into its flight to Beijing, but this information was not made public for many hours. Malaysia has faced accusations of not sharing all of its information or suspicions about the plane's final movements. It, however, says it would be irresponsible to narrow the focus of the search until there is firm evidence of the plane's flight path. Malaysia's reluctance to go public with the news that one of its planes had vanished is perhaps understandable. The disappearance of the Boeing 777 – one of the safest commercial jets in service – is one of the most baffling in aviation history. It is extremely rare for a modern passenger aircraft to disappear once it has reached cruising altitude.

Why did no one see the plane veering so far off course?



They did. The New York Times, quoting American officials and others close to the investigation, said radar signals recorded by the Malaysian military appeared to show the airliner climbing to 45,000ft, higher than a Boeing 777's approved limit, soon after its disappearance from civilian radar, then making a sharp turn to the west. The radar tracking then shows the plane descending unevenly to 23,000ft, below normal cruising levels, before climbing again and flying north-west towards the Indian Ocean. What the military did with this information is not known.

Why this flight?



Here we enter the realm of wild speculation: the internet is awash with theories. It could be that Malaysia was geographically convenient. Some suggest that, if it is a hijack, it is probably the work of Uighur separatists in Xinjiang, western China, or Islamic terrorists. On 1 March attackers armed with knives killed at least 29 people and injured more than 100 in Kunming station in southern China. Chinese authorities and state media were quick to describe this as a terror attack by Uighurs in their "jihad". Hijacking a plane would be by far their most spectacular achievement. The plane had fuel to get as far north as Kazakhstan, according to some experts, which means it could have been flown to Pakistan or Afghanistan. However, given that the jet was not detected by these two militarised countries, this seems unlikely. Some say a flight from Malaysia to China was a softer target than, say, a transatlantic flight, but there is little evidence for this. There are, say pilots, many softer targets.

Why are the pilots' homes being searched only now?

This does raise questions about Malaysia's handling of the situation. The lengthy delay appears to bolster criticism that Malaysia has been ineffective in this crisis. Numerous false sightings of wreckage may have convinced the authorities that they were dealing with a disaster, not terrorism, which could explain why they did not immediately search the men's homes.

Why did Vietnam not raise the alarm?



Once an aircraft is more than 150 miles out to sea, radar coverage fades and crews keep in touch with air traffic control and other aircraft by high-frequency radio. About 40 minutes in, the flight was still the "property" of Malaysian air traffic control, which we know made contact with the plane minutes before it disappeared. All seemed fine as the pilot reported "all right, good night". This last verbal communication came at the boundary between Malaysian and Vietnamese airspace. Malaysian air traffic control told the pilots the flight was being passed to Ho Chi Minh control. The Vietnamese authorities may never have assumed responsibility for the plane as it never entered their airspace. This would be consistent with where the search has now moved to.

How do investigators know the communications systems were shut off and did not just go wrong ?



This is based on information from the Malaysian authorities who, admittedly, have given contradictory reports. The prime minister, Najib Razak, said investigators now had a "high degree of certainty" that one of the plane's communications systems, the aircraft and communications addressing and reporting system (Acars), was disabled before the aircraft reached the east coast of Malaysia. Shortly afterwards, someone on board switched off the aircraft's transponder, which communicates with civilian air traffic control.

How do we know the plane flew on after the transponder was switched off?



Routine, automated signals from the aircraft – known as electronic handshakes or pings – registered on the Inmarsat satellite network. MH370's last ping suggested it was in one of two flight corridors: one between Thailand and Kazakhstan, and another between Indonesia and the southern Indian Ocean. The last confirmed communication was at 08.11, which would indicate that the Boeing continued flying for nearly seven hours after contact was lost. So its location will be extremely difficult to pinpoint. Without further radar/satellite/eyewitness testimony, say experts, it is very much like looking for a needle in a haystack. A source familiar with US assessments of the Inmarsat pings said it appeared the plane turned south over the Indian Ocean, where it would presumably have run out of fuel and crashed.