AC offers free WhatsApp, iMessage, messenger in most flights. You can ask meta through WhatsApp to effectively browse the net :)
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At a certain provider, all those free logins used the same firewall configuration to only allow traffic to those free services and ISP site, probably for simplicity, so all of them were accessible with any promotional login. Most of them were not useful (to me), but different agreements with ISP resulted in different call time limit until hang-up, 10-15 minutes instead of 3-5.
However, the main treasure was the addition of external page translation service as a feature on some big site. Back then, it was strictly static and server-side, URL in request gave you its HTML source with translated text strings and absolute paths to external resources, so in order for translation to work, users needed to be able to access that third party server, too. Obviously, if you gave it any other URL, the server would also grab it to translate (and choosing least similar language in parameters would leave most of the page text intact).
You can imagine that having a browser supporting tabs and switching media off was very handy for loading as many free web pages in text only form as those dial-up sessions allowed.
Obviously, WWW-to-email services for people who only paid for mail server access had existed even before that.
With Starlink things may be looking a bit better, but I think demanding net neutrality on in-flight satellite internet and plane-to-cell-tower internet is excessive.