Isn’t this data meant to be exposed? You can get all this flight status on the Southwest intranet when you’re connected to WiFi as part of the flight status page.
This hack just goes a step further to plot the data over time.
The concern isn’t access to the flight status data (or even your data, which is most likely encrypted these days), but theft of service you paid for, by another passenger on the flight (you would probably at least get kicked out/experience issues with your own connectivity, and might worst-case be blamed if something bad happens using the connection you bought).
I used to play with IP-over-DNS, which more or less worked on an awful lot of these plane wifi systems. Haven't tried it in the past couple years though; it's always slow the point of barely being usable. You can probably get your mail via IMAP if you're patient and nobody's sending you large attachments, that's about it.
This hack just goes a step further to plot the data over time.