I guess as soon as you're flying upwind it can. I can see what you're saying as long as you're flying downwind, although that probably assumes nice non-turbulent flow.
However, in the "flying next to a mountain" scenario you won't be flying upwind or downwind. You will be flying across the airflow (i.e. parallel to the mountain face). The wind is coming down the mountain, so if you did fly upwind you would fly into the rising ground (not good).
I imagine too that people have been caught out by believing they could go over a ridge in a windward direction because they were above the ridge to start with. In this situation they may not have had the climb rate to maintain their altitude as they approached the peak, cutting through the descending airflow
Absolutely agree. I just couldn't see how descending airflow could force a plane all the way into the ground - unless there are other factors.
As to those having a go at me over suggesting that a GPS should be switched on if it is being carried at all, I am suprised as some who did should definitely know better. A GPS in the bag, not switched on, is about as much use as a chocolate teapot.
I am trying to write stuff that expands knowledge on a subject. If everybody did the same it would be helpful all around. If somebody disagrees, it's better to post a good reasoned argument which I can learn something from, not Oh for F*CKS sake!