I use a Motorola DynaTAC 8000X. It's a little heavier than some of the newer phones, but it works great.
That was in the days when few had cell phones, and so you could use them on flights. I found by experimenting, that as I was coming into a metro area, they would start working as the plane descended, about the time we hit 10,000 ft and below ...
They work great for you because you have 3 watts of power as opposed to what, about 1/2 watt with todays pocket warmers?