Bad idea to get a facial (this includes extractions) before a flight?
Yeah, probably bad idea to stress out your skin before a flight.
I concur with everyone on the hydration front. I would also recommend getting some sort of hand sanitizer if you're the type that touches your face a lot. I always end up touching my face all the time, which causes skin irritation and the odd in-flight pimple formation. So hand sanitation can help prevent that.
I love the Evian spray mentioned above too. It's pretty affordable and is seriously refreshing. I also love Caudalie's
Beauty Elixir, but it's much more expensive ($49). I got it as a gift, so I've been rationing it.
Also, I would suggest a spray on dry oil. It moisturizes without you having to touch your face.