Why does the Flight 370 search area keep shifting?

Crews are searching for Flight 370 from the air, on the ocean's surface and underwater. They are combing a new area of the Indian Ocean. Authorities have changed the search zone several times. Tom Foreman explains why it will likely move again.

John Berman discussed all of this with aviation analyst Miles O'Brien, aviation correspondent Richard Quest and CNN analyst David Gallo, co-leader of the search for Air France Flight 447.