Has anyone had experience of flying or attempting to fly through tunnels... in particular disused railway tunnels...? An attempt was made and it responded and flew fine until after about 30m away when it failed to respond correctly and all it could do was drift sideways when trying to fly forward (in fact it clipped the tunnel wall). I had complete line of sight of it and as said was only 30m away. I tried disabling collision avoidance and got same effect. Obvioulsy it didn't have any GPS signal, but can't they fly indoors where GPS would be lacking too, or is it complete lack of GPS is where the issue is, and is there anyway round it? There's not much I can find on operating in tunnels, maybe I have answered my own question (lol)!