If you're on a long flight, do yourself a favor and catch some zzz's! Take the time to sleep, instead of (or after, let's be realistic) watching a movie. Sleep is good for your skin and immune system. If you're always waking up with a crick in your neck, try out the Trtl Pillow, $29.99. It's basically a fleece dickie, with an internal support system to support your neck. It doesn't take up much room and is machine-washable.
Bad news, the recirculated air in planes is full of germs. Good news, you can fight off those nasty illnesses. Help your immune system with a couple of drops of Rejuvica Health MunoMax, $34. Packed with proven immunity boosters like echinacea, turmeric, and elderberry, it's a must-have for flights.