Hopefully by now you're feeling better! Once when I had to fly despite terrible head congestion, my doctor recommended Sudafed on the night before and every 4 hours the day of flying and then use of saline nasal spray followed by OTC neosynephrine nasal spray. Use the sprays 30 minutes before takeoff and landing (disregarding the 12-hour instructions on the box - this is to be used only on the day you have to fly, so apparently it's ok to exceed the normal recommended dosage) and every 4 hours in flight if you're on a longer trip. Make sure you're also drinking lots and lots of water, herbal teas, or juices (not sodas and coffee) if you're battling this kind of congestion, particularly in the dry air on the plane. If you take Afrin as recommended by another FT'er, please be cognizant of its slightly addictive nature - don't take longer than 3 days.