With rare exception I never work on a plane anymore, I'll watch movies, I'll read a physical book, but in general I use it as a time to refresh and unplug for even just a few hours. The two exceptions are for short flights when I am going to do a presentation or similar and only on a plane for an hour or so, then I'll go over my presentation etc. Or on the long international flights (16-20 hrs in a plane), I'll generally stick to my no work policy but sometimes do enjoy learning/practicing a new technology during that time, and I do not use plane wifi pretty much ever.
The learning/practicing a new tech without having access to Google & Stackoverflow is a good way to force yourself through reading API's etc (I usually download API docs/libraries ahead of time). So this takes a little preplanning but I find I learn things better and retain them better than if I had access to Google/Stackoverflow et al. If you want to call it a hack, this is probably my "plane hack" since it lets me learn a skill or toolset better then if I was connected to Internet.