Actually, no. I tested my G1, in airplane mode, both on a commercial flight (at FL350) and in a single-engine Cessna (at 2500AGL), and in both cases, I was able to acquire and maintain a steady GPS lock, and even recorded a track in Maverick. The altitude was WAY off - it'd jump from 38,000' to 12,000' in a second, for example - but latitude and longitude both tracked quite well.
This is by no means indicative of GPS-equipped cell phones in general, of course.
As per battery and charging, there's always a MintyBoost or some such, attached to a small 6V PV cell.