I've spent 175 hours on long-haul flights. These are the most essential items to keep in your carry-on.

A refillable water bottle is a must to save money — and plastic — on disposable bottles.

The air on flights is very dehydrating, as Business Insider previously reported, and I feel that acutely on longer flights.

I also bring lip balm to keep my lips from getting dry.

Since lip balm is so small, I typically bring two or three in case I lose one.

To keep your skin hydrated, I recommend slipping some lotion in your carry-on, too.

Some long-haul flights I've taken have had lotion and face mist in the cabin bathrooms, but I wouldn't count on it.

You should also bring Advil.

Dry air on planes could cause migraines, BI previously reported.

A toothbrush is a must.

Some of my trips have been so far away that I had to take three long flights over a 24-hour period. I don't normally go 24 hours without brushing my teeth, and if you don't either, I'd suggest bringing a toothbrush.

Though it won't satisfy a craving for clean teeth, a pack of gum is always helpful for fresh breath.

Gum also helps combat ear-popping during changes in air pressure.

I recommend bringing a change of clothes — especially if your trip has layovers.

You may get sweaty, depending on your flight's temperature.

In the same vein, deodorant is essential for these long trips.

I typically reapply deodorant in airport bathrooms during layovers.

Long flights can be the perfect time to sleep, if you bring some comfort. Thankfully, my step-grandma gifted me this neck pillow for Christmas two years ago.

It's not your average neck pillow — it wraps around your neck 1.5 times. This makes it much easier to find a comfortable position to sleep in a tiny plane seat.

If a pillow doesn't do the trick, a sleep mask is a total game-changer.

This is especially helpful for flights during the day. But even on red-eye flights, sleep masks help me block out the lights coming from passenger seat-back screens.

If you're unable to nap, bring entertainment, as some flights don't have tablets on the back of each seat.

I suggest downloading movies and shows onto your phone or tablet.

If you wouldn't be satisfied with just TV as entertainment for several hours, I also recommend downloading books and podcasts to pass the time.

I typically download travel guides for the destinations I'm visiting. 

With all this power being used, be sure to pack an external battery charger.

Most long-haul flights I've been on have had outlets at each seat, but I always back a battery just in case.

Long-haul flights are typically the most grueling and boring aspect of my trips, but I think having these items make them a little more bearable.

In my experience, long-haul drives can be as grueling as flights. So check out these tips on what to pack for a road trip to make your journey run smoothly.