Some relatives of survivors are reporting that their loved ones phones are ringing, then apparently being hung up. If this is correct, then the plane may be down somewhere but under the control of somebody who does not want the passengers communicating. If the plane is under water, it's extremely unlikely that any cellphones onboard would still be working unless the water is very shallow and parts of the aircraft haven't been flooded. It's difficult to tell from the stories if the phones are actually being picked up but then hung up, or if they are ceasing to radio back, or if the calls are being sent once to what central switching units had recorded as active cellphones while the plane was in the air, but which it switched to inactive when they weren't answered.
Nevertheless, the apparently still-functioning cellphones are part of the mystery of the flight, and another source of agony for waiting relatives.
For more on this, click here.