It has been more than four days since flight MH370 disappeared from the skies, and left the world praying for the 239 people onboard. And as time passes and lines of inquiry turn into false trails, the mystery of flight MH370 becomes increasingly bizarre and baffling. Weather conditions in the area were reported as being fair at the time the plane went missing, and no debris relating to the plane crash has been found.

So what could have happened to the flight MH370? We look at the possible scenarios…

Technical failure: All eyes were on the Boeing 777-200 aircraft following the crash, but there is no indication to show the aircraft had any technical problem. Wing-tip damage suffered at Shanghai Pudong Airport two years ago was repaired and is unlikely to have been a factor, and there were no distress signals prior to the disappearance. The B777 has one of the best safety records of any passenger aircraft in aviation history, and if it had crash landed in the sea, where is the wreckage? Even after the 2009 Air France crash in the Atlantic Ocean, wreckage was located within a few days.

Terrorist attack: The spectre of terrorism has been raised by the revelation that two Iranian passengers onboard the flight were travelling on stolen passports. But Interpol has since said that neither man had a criminal record and both were travelling onwards to Europe. And while it wouldn’t be the first terrorist incident that lacked a claim of responsibility, it is strange that terrorists would not want any publicity from such a high-profile incident. Finally, if the aircraft exploded mid-flight, like the 1988 Lockerbie disaster, the wreckage would have been strewn far and wide.

Hijacking: Again, the presence of two men travelling on stolen passports appeared to heighten the possibility of a hijacking. But if the aircraft was stolen, where was it taken to? Boeing 777s are too big to land on remote jungle air strips, and airports would surely notice an unscheduled wide-body landing. And if hijackers are holding the passengers hostage in some remote location, where is their list of demands? This is the hope that many people are clinging to, but sadly it seems an unlikely scenario.

Failed terrorist attack or hijacking: It is possible that any attempted to take control of the aircraft could have been met with resistance from passengers and crew. The most famous example of this of course, was United Airlines flight 93, which was overpowered by passengers on 9/11. This could account for the aircraft changing direction before it dropped off the radar. But it doesn’t explain what happened to the aircraft afterwards.

Pilot suicide: This is the one theory that no-one wants to contemplate. But it has occurred in the past, including the crash of a SilkAir flight in Indonesia in 1997. It would explain the apparent lack of technical problems with the aircraft prior to take-off, and the aircraft’s disappearance from radar could have been caused by the transponder being deliberately switched off. But it still doesn’t explain the lack of crash debris, unless the pilot veered sharply off course.

With the search for the missing aircraft being expanded to include increasingly vast swathes of the South China Sea and Malacca Strait, along with the mainland of Peninsular Malaysia, the huge international operation to find flight MH370 could go on for several weeks yet. And until the aircraft is discovered and the flight data recorders analysed, the cause of the incident is likely to remain a mystery.