Are you more likely to be exposed to germs on an airplane because of the recirculation of air? No, according to Wired, because the air is very well filtered and constantly exchanged with outside air. Now, I too have gotten that cold right after traveling. So I probably got that cold from something I touched at the airport T.G.I. Fridays. So the moral of the story, I think, is always remember to wash your hands at the airport before you pick your nose. Other theories I have come up with, without trying to collect a shred of scientific evidence, is that the dry air on planes dries out your mucous membranes so there is less of a barrier to germs, and/or that the general stress and lack of rest when you travel just wears down your body’s defenses to the ordinary garden-variety germs you encounter every day.