Timely. I've been noticing on flights that the in-flight wifi uses a squid proxy to block you until you pay - but most of the time, you'll get whatever data from the DNS Forwarder even if you haven't paid yet.

I've been noodling on how to build a simple proxy off DNS to test on my next flight.

Otherwise there's https://github.com/yarrick/iodine

Edit: seems like others have recommended it already. I got it working in a hotel room once after giving up on the utterly broken ToS acceptance page for the WiFi.