One of my friends admitted to me that he couldn't understand why someone would want to sit in a "tube" for 12+ hours. My response was: "Well, we all basically sit, either behind a desk or on the couch for about 12 hours a day, so why not do the same while on the way to someplace cool and exciting?"
I travel a lot, so over the years I've settled into a routine in order to maximize my productivity and comfort while en route to another city or country. So I'm not just sitting in a tube for 12+ hours, but I'm mimicking a productive workday and/or a relaxing weekday catching up on movies and T.V. shows.
Long Haul Flights
Before I board a long haul flight, I make sure that I am hydrated and am wearing comfortable clothes. I don't want to look like I'm about to go to bed at home, but I also don't want to be fashionable at the expense of my comfort. So I usually settle for some middle ground and wear lounge pants that don't look too much like pajamas, a trendy cotton fitted tee, fuzzy socks, and a long, loose cardigan. Also, I will bring my Hello Kitty neck pillow and a sleep mask for neck support and to block out the light while I sleep, respectively. Airplane seats, especially in coach, aren't the most comfortable so I try to make sure that my clothes allow for ample movement so that I can get into an optimal position for sleep. Also, it is important to get on the same sleep schedule as the place where you are going. For example, I may board my 12 hour flight at 11:30pm but it is 11:30am at my final destination, so I will try to stay up as late as I can so that I am falling asleep right around the time that people at my final destination are falling asleep. Once you arrive, it is imperative that you stay awake (no napping!) until the evening, otherwise your sleep pattern will be off for the duration of the trip.
If I know that I'm going to shop 'til I drop, I will bring an extra empty suitcase to fill up with goods from the markets because most airlines allow up to two free checked bags for international flights. My favorite markets are the Souks (Dubai), Feria de Recoleta (Buenos Aires), and the Chatuchak Weekend Market (Bangkok).
Most international flights have personal in flight entertainment with many movie and music choices from around the world. Some of my favorite in flight discoveries are: Rebecca Ferguson, Vanessa de Mata, Miss Granny, and Twenty Something. So explore away! You never know what little known (to Americans) artists you will discover and add to your playlists.
Short Haul Flights
I frequently travel from NYC to Ohio and Florida, and even though it's only a few hours flight, I still like to be comfortable and productive because you always need to be prepared for delays and cancellations. I always bring a book or magazine to read, my laptop in case I need to update spreadsheets or presentations, and a portable battery charger as well as the plug in kind. In terms of my clothes, there's no need to be as comfortable as if I was on a long haul flight, but I still prefer to wear loose fitting clothes with breathable fabric. My favorite travel outfit (see photo) consists of ankle boots with a low heel, stretch skinny jeans, Exclusively Kristen's Supportive Tank Top, and a cardigan.
For both short and long haul flights, most airlines provide in flight internet service for a fee, but be sure to read the fine print so that you don't end up like this guy.