What I don't understand (and there must be an explanation, so please inform me if you know) is why, with 1) GPS tracking and 2) satellite two-way communications available, there are times during a transoceanic flight when a commercial aircraft is out of range of tracking and out of communications. Why should there not be a telemetry stream of all the data a flight data recorder captures, thus giving the NTSB or similar agencies something to analyze even if the aircraft is unrecoverable?

(ETA: Looks like flyinbob and I had the same idea...surely we can't be the only two.)