Many years ago (2012) Delta inflight wifi would allow DNS queries out without paying. Being a very frequent flyer I used to run an ip-over-dns tunnel using Iodine[1]. It was slow but worked. I wonder if they’ve blocked that hole yet.
When selecting my personal use domain I ended spent some time finding a short domain partly because it's convenient but partly because it meant more goodput via Iodine. I ended up on "ds.gy" as ds are my initials and it was the only TLD that domain wasn't sat on by squatters wanting to charge thousands.The ratio of people wanting to sell you short domains vs actually using them in any capacity was surprising.
I did the same on trains in the 00s, but built application specific tunnels which were much faster, funnily enough among them was one that would fetch Wikipedia pages. The client would piece together the replies and render the markup to html again.
I can confirm that this still works on several US airlines especially if they have a free messaging option.
I tried Iodine around 3 years ago on a Swiss flight, it worked to read my mails over SSH using Alpine, but was so slow that basically it was unusable. Not sure what was going on, I had the impression that DNS queries were getting throttled after some threshold...
Check Mosh, Mosh works on ISDN level speeds.
I also used this a lot while travelling to access the internet through captive wifi portals. Especially in asia this worked very well, given the huge amount of telco wifi providers in cities.
lol holy shit I'm never going to have an unproductive flight again