It might help if you said what kind of a gaming platform you'll have on the plane. Laptop? Tablet? Phone? What operating system? My games for example don't work on mobile devices, and most have very short play times of 10-15 minutes. They are, however, all free, and all but one are complete if minimal. Do you mind abstract or ASCII art? If you can narrow it down a little, I can likely pick one or two for you.