I thought I'd post the results.
Verizon issued a replacement phone. It takes quite a while to get it set up the way I want it, but it seemed fine. I even upgraded the new phone to .215. So far, so good.
So, today I took it flying again, just a little hop. The phone was all charged up and I was only going on a 15 mile flight. The top speed 165 mph , the highest altitude was about 1,500 ft. above ground level, and I was in the air about eight minutes. Like I say, just a little hop from one airport to another.
When I got on the ground, the new phone was deader than a door nail. Nada. Kaput. Zero. And again, the phone was completely cool. When I pressed the power button, nothing would happen. Nothing.
I needed to make a safe arrival call and I had a charger with me, so I went to the pilots lounge and plugged it in. The M came up, then the 0% charge, then in a few seconds the 5% charge indicator. Then I pushed the power button and it booted up normally.
Then something screwy; the GSam Battery monitor said I had about 89% charge! I then unplugged the charger, and the charge remained at about 85%. It was plugged into the charger for perhaps three minutes.
I have been using the phone for the past seven hours, and it has been just fine, still reading 65%.
So, I think there is some sort of logic that tells the battery to shut down and for the phone to go dead and that battery is indeed fine. Maybe it's something installed to force phones to quit when flying in airliners. Maybe it has something to do do with being at higher elevations, but if this was the case, I would think that the phones wouldn't work well in mountains just above cities. 1,500 ft isn't all that high. Maybe it happens when it's in some kind of roaming situation. BTW, this is in downstate Illinois, lots of very small towns and two towns with a combined pupulation of 50,000, so it's not exactly an intensely congested area.
When I first reported the problem, the tech suport at the Big V had no idea what was going on, so I suppose it's their secret.
Going forward, I'm just going to consider this a characteristic of the phone and learn to live with it. I guess I will add "Turn off phone (or place in Airplane mode)" in my pre-flight checklist. One more thing I could try, is to plug the car charger into my plane's electrical system and see if that makes any difference. I do like to text my wife when I'm in the air to keep her informed of my position.
So, strange, eh?