What happened to the plane is still a mystery but we are starting to find out important details as days go by. Malaysia Airlines Flight MH370 lost all communications, including transponder signals at 1:30 a.m. A transponder is a radio transmitter that works with the ground radar. It is located in the cockpit. When it receives a signal from a more sophisticated ground secondary radar, it returns a four-digit identifying code that the pilot enters into a transponder for each flight also known as the squawk code. This helps air traffic controllers on the ground determine the plane’s speed and direction.
After losing communication, it still appeared on the radar for one hour and 10 minutes approximately, then it vanished. But still many questions remain. Mark Weiss, a former 777 pilot said "Something happened to that airplane, that was obviously out of the norm, that caused it to depart from its normal flight path. It’s not difficult to speculate.”
CNN law enforcement analyst said "There are still as many possibilities out there, maybe more, now that we know about the transponders being off and the length of time that plane flew in the air without them. It still leaves mechanical, terrorism (and) other issues as much in the air as they were before."
Apparently the plane’s transponder stopped working at the same time flight controllers lost contact with it and that was near the coast of Vietnam, according to Malaysian air force officials. The air force official also said they totally lost track of the aircraft over Pulau Perak, a small island in the Straits of Malacca, hundreds of miles away from the usual path the plane would have taken to get to Beijing.