Everything already mentioned helps shorten the duration. If you have the want to relieve the symptoms so you are not the ONE on the plane coughing and sneezing I like Vicks cold & FLu and Alka Seltzer cold relief. I'm sure there are others and some of them may give you the " medicine head " but they do relieve the symptoms and should help.
Good Luck

Side story - I wish a woman who sat behind me at dinner one evening last year had taken something. It was out side with low lighting. She sneezed all over my neck and shoulder. All I could see was the particles glistening in the light as it was spraying over my left shoulder. She never said a word! I got up, went to the rest room and tried to clean up the best I could. Thank lord I did not get sick