I've seen a few fires that I hypothesised were field fires but couldn't confirm.

For me, FES does not give me permission to fly over unlandable terrain. Yes it's quick and pretty reliable but I'm not betting my life on it and not risking the glider.

The thermal was at the edge of town, plenty of fields around. Uli was under me and ended up in a nice cut wheat field a few km outside if town so that is a good indication that we weren't soaring Iver unlandable stuff.