It was never wildly off of its flight path when the transponder quit.
On March 11th CIA Directer John Brennan “confirmed reports” that Malaysia Flight 370’s transponder “had been disabled or turned off at some point during the flight” and said he is not ready to rule out terrorism as the cause behind the plane’s disappearance.
According to ABC News, Brennan was speaking to the Council on Foreign Relations when he said these things.
He said:
[There have been] some claims of responsibility that have not been confirmed or corroborated at all. We are looking at it very carefully. We, the CIA, are working with the FBI and TSA and others. Our Malaysian counterparts are doing everything they can to try to put together the pieces here. But clearly this is still a mystery, which is very disturbing.