What follows is a multi-pronged anti-aerosinusitis campaign strategy. To start with, some anti-bacterial wipes or hand sanitizer should help take care of the microscopic zoo festering on every surface you touch while airborne. Also, stay warm. The interior of a plane is often chilly. If you cool down too much, it could dial down your immune system.
If you have sinus trouble because of a cold or allergies, consider an oral treatment like a SUDAFED® decongestant, which should be taken about an hour before you fly. It won't cure your cold, but you should have less stuffiness as your baseline before you take off.
If you don't have any sinus problems, try to keep it that way by irrigating your nasal passages with a saline solution before, during and after flight. Also, drink as much water as you can to stay hydrated, which will in turn help keep your sinuses from drying out. For similar reasons, bring some herbal tea and breathe in the steam for 15 minutes or so.
And watch the caffeine intake. That coffee you're considering is a diuretic, meaning it makes you pee more, which can dehydrate your body, which, in turn, is terrible for your sinuses. If you must have that cup of coffee – and some of us really, really must – drink more water to make up for what you'll be losing ... even if it may mean squeezing past your seatmate to go to the restroom in flight.
To equalize the pressure in your head with that in the cabin during liftoff and landing, there's a trick known as the "modified Valsalva," which involves pinching your nostrils, swallowing and blowing gently into your nose, in that order. This can be repeated throughout the flight [source: Bennett]. Yawning, swallowing and chewing gum can also help.
Finally, try to avoid sleeping through lift-off and landing, because if you're asleep you won't be able to practice that fancy Valsalva maneuver or yawn and swallow obsessively. If you're so exhausted you know there's no way you'll be able to stay awake for take-off, you can pick up a pair of special, filtered earplugs, which help equalize the pressure in your eardrum. That, in turn, should make things easier for the old Eustachian tube and all the little cavities it connects to, including your sinuses [source: Mayo Clinic].
Sinus Congestion Tips
Here is some information to help you with sinus congestion.