. The night time is more sleeping, and hey even if you're travelling during a night that planes are the absolute worse place to try to catch any more than 30 minutes sleep, so get productive.
I seriously recommend that you use the time when you're on a flight to do something productive. Often, I'll take my laptop on board a flight and try to get some work done. Before you book flights from New York to Albuquerque or decide which flights from New York to Delhi will work out cheapest you should also consider which planes have both plug sockets so that you can charge your computer and which flights will have in flight WiFi that will enable you to work online.
Even without WiFi or somewhere to charge your device there is plenty that you can do to be productive. You can look over that long report or research project and try to think of a second way to make the argument, or simply go through the whole thing and eliminate any spelling mistakes that have crept in. I also like while I'm travelling to take the opportunity to reorganize the files on my computer and do a little digital spring cleaning. It means that when you do come to actually have to do some work you will be in a much better position to do that work effectively.
The final thing you can do to be productive is to actually put the computer away and read a book. Flights from San Juan to Boston will pass much more quickly if you take the time to read and actually learn something in an environment where you will not be disturbed by the phone or by email notifications popping off. That's the sort of productive pass that's very valuable and you should seize.