Why do I need moisturizers for? I had experienced a 5-hour flight and didn't crack my skin!
I've done a number of flights v.v. from jakarta to US (total flight time is 30 hours plus, depending on the route and the city destination. My record was 34 hours from jakarta - seoul - St. Paul/minneapolis - washington DC), europe (16 - 18 hours), australia and north east asia (around 8 hours), saudi (10 hours), and even flights to the remotest area in Indonesia (papua) take around 7 hours total.
For me the most unpleasant thing about long haul flight, by far, is always the very dry cabin air.
I don't have problems with flights up to 5 hours, but the long haul flights always made my skin very dry, and I often had trouble breathing if it is too dry. So, if you have trouble breathing in very dry air, you need to bring something like saline nasal gel to hydrate and make the inside of your nose moist.
Remember that the cabin air is totally re-cycled through air conditioner, make it more dry the longer it goes. So apart from moisturiser, you might also want to bring lip balms.
And drink plenty of water, because your body gets dehydrated a lot quicker than normal. Ask the flight attendants to give you a bottled water or two. avoid acidic juice like orange juice or caffeine (which dehydrating). I've heard tomato juice is great for long flights.
wear comfortable clothes.
You might also want to bring your own hand wipes or hand sanitizer because there are plenty of germs in the plane, especially in the loos (which are shared by hundreds other passengers).