Good point. I oversimplified. Birds and pilots tend to not fly up into clouds for visibility reasons but the air keeps rising into the cloud. From experience, i

Good point. I oversimplified. Birds and pilots tend to not fly up into clouds for visibility reasons but the air keeps rising into the cloud. From experience, it's a surreal experience riding a thermal up into a cloud in a paraglider. Just not safe or legal in most places to stay in the cloud.