On the sixth day after MH370 disappeared, there was still no further information on the airplane's location. Why have the authorities and airline from Malaysia changed the time of disappearance and the last-known location of the airplane again and again?

A China Daily reporter interviewed some civil aviation experts and senior captains on key questions.

What are possible scenarios?

A senior captain from a domestic airline: "There are so many possibilities as the information from Malaysia is still not clear. Some of the current deductions might even be very scary."

Special: Malaysia Airlines plane missing

Chen Cheng, chief editor of Sina.com's aviation channel, who also was a maintenance technician for Boeing 767s for five years, said: "I cannot make a guess before we even see any debris." What about having been shot down? "Generally speaking, if the air force notices an unidentified flying object in its airspace, they will send a fighter plane to observe it rather than shoot it down directly."

Another senior captain: "My first thought was terrorist attack, and later, I feel it might be decompression, in which the crew would lose consciousness in a short time. But now, it is so difficult to analyze what happened, after so much different information."

Which automatic means of communication could the airplane use?

Malaysia Airlines: "All Malaysia Airlines aircraft are equipped with a continuous data monitoring system called the Aircraft Communications Addressing and Reporting System (ACARS), which transmits data automatically. Nevertheless, there were no distress calls, and no information was relayed."

Chen: "All the airlines, the airplane manufacturer and the engine manufacturer have their methods to get real-time data from a flying aircraft. But they cannot release it to either the public or the media, as they provide the data to air accident investigators now, according to regulations from the International Civil Aviation Organization."

Why can't we get clear information more than 100 hours after the airplane disappeared?

Albert Tjoeng, assistant director of the International Air Transport Association's corporate communications division in the Asia-Pacific region: "This will be one of the key questions that needs to be addressed as part of the investigation process."

Chinese captain: "There are too many doubtful details in the whole thing. We can believe that the local authorities have problems with cooperation and communication, or someone is trying to cover up some truth."

Did you notice any doubtful points?

Chinese captain: "It is reported that the airplane was flying at a height of 29,500 feet on military radar, although the Malaysian air force denied the report. If it is true, it means the plane was manipulated by a very professional pilot, as the height is different from other airplanes' routes and great care would be needed to make sure a plane without a transponder would not collide with others."