Do some exercises in your seat

Sitting in one position for hours on end is not good for your body. In fact, there have been multiple reports of people getting blood clots after a long flight. One of the best ways to avoid this is doing some exercises in your seat. Research the easiest exercises to do from a sitting position.

Listen to music

For many people, music is the soundtrack to daily life. You might play it when you are working, cooking, cleaning up, or walking. However, how often do just listen to music and do nothing? Actively listening to music like this can open up a whole new world of enjoyment. Listen to the different instruments and allow your mind to wander. You should also consider listening to some new genres of music and expanding your taste.

Visit an online casino

If you are a fan of games like poker and blackjack, you should definitely visit an online casino. You can choose from a bunch of different games, gamble with real money, and play against other people. If you are a fan of gambling, it is a great way to pass the time. Be warned though, you should practice safe gambling practices and only play with money you can afford to lose. 

Surf Wikipedia

Wikipedia is one of the best tools on the internet. You can find information about pretty much any subject in the world, although not all of it is 100% accurate. To pass some time, you should browse through the articles and see if there is anything you are interested in.

Listen to a podcast

Podcasts have become immensely popular in the last decade. It is now the go-to form of content for comedians, celebrities, and pretty much everyone in the public eye. If you are interested in a subject, you can almost guarantee that there will be a podcast on the subject. Check out the most popular podcasts in the world and go from there.

Do some crossword or Sudoku puzzles

To pass time successfully, you need to find something that truly engages your brain. That is why crossword puzzles and Sudoku are so effective. It can take up to a couple of hours to complete one, and your brain will be engaged the whole time. You might find that you get obsessed with puzzles and become an avid puzzler.

Get paper & pen and write

You should think of a long train journey as an opportunity. How often in life do you have a period of time with absolutely nothing else to do? Not very. So, if you have always liked the idea of becoming a writer, why not use this as a time to try it out. Get a notebook and a pen and just start writing. Start with a short story or a diary entry and go from there. Who knows? You might discover a talent that you never knew you had.