We don't spend too much time thinking about it, but most of the time, our Android phones and tablets are online: Whether it's through a Wi-Fi connection or a cellular data connection, there is a constant flow of data between the device and the Internet. That is, until the connection breaks for some reason... and the games you love stop working.
That's probably not something that's going to happen at home, but it definitely might happen when you're traveling -- not to mention when you're flying, of course. The best thing you can do to prepare for this is figure out which of your games work well offline, and which of your games absolutely require a connection and won't work offline. You could even make an "offline games" folder on your homescreen, ready for your next flight.
To test whether or not a game works offline, all you need to do is completely disconnect your phone or tablet from any sort of connection. Don't worry -- you don't have to open it up or do anything tricky. The only thing you need is Airplane mode, a feature every device has.
To test whether a given game works offline, do this:
Many games work flawlessly with no connection. In fact, some games are even better when played offline, because the game itself works well but no ads are being displayed (because displaying ads requires a connection).
And one last tip: Some devices offer quicker ways to switch on Airplane mode, such as a status-bar toggle. If you're looking for an app to toggle such settings, you should try out Quick Settings.