I read arvix papers and all the other tabs I have open that I've been meaning to read). These days, that means I need to purchase WiFi unless I take time to specifically download PDFs. (Because <gesturing vaguely around at the complexity of our current web stack from top to bottom>.) But it's a kind of work+pleasure that is usually a little more flight-compatible for me than, say, writing code or in-depth text.

I'm on a flight right now. So I guess I also read HN on flights. :-)