I've had mine go off a couple of times above 30,000 feet when I've forgotten to turn it off.

But my most remarkable long range experience was in a rental car driving through central Kansas a few years back, hearing my phone ring, then discovering later, after the call dropped, that I was getting a cell from Oklahoma....over 100 miles away.

At first, I thought the call was just being routed through Oklahoma. But when I contacted my provider concerning credit for the dropped call, it was established that the tower I'd connected with was indeed in Oklahoma.