I keep technical videos on my laptop for these times. On a short flight, my preference is just to sleep. I am more likely to watch the videos during all the interminable waiting that surrounds a flight, when you can't safely fall asleep, or on a long flight if I wake up and get bored, or if I am staying awake waiting for a meal. Today I'll be giving Link some exercise stocking up on just-released PDC videos before my transatlantic flight tomorrow.
For years I spent time every week at events for my kids where there was no wifi but I didn't have any real duties - I bring the child, I can watch if I want, but there's nothing I need to do. I developed the habit of saving certain of my todo's for that time. Revewing a document someone else wrote, or typing in a stack of paper notes I took during a meeting, or making a good copy in Visio of a diagram from a whiteboard that I photographed, that sort of thing. These are also highly interruptable should my child suddenly do something interesting that I want to pay attention to. If you have this kind of downtime regularly, pay attention as you go through your regular workload and ask yourself "could I save this for Tuesday night?".