The common cold has yet to be beaten by medical science. But, a new journal article shows that commercial airline flights dramatically increase your risk of getting a cold. The risk of getting a cold is conservatively estimated at sixty times as great as it is on the ground. Analysis of the data revealed that this was most likely due to low humanity and an absence of outside air, rather than from recirculation of air in the cabin. Providing outside air would cost about 33 cents per passenger per hour. Humidity would also not necessarily be very expensive. As a stop gap, face masks like those worn by surgeons and nasal sprays look likely to be effective (although their efficacy was not tested in this study).
Hat Tip to NewMexiKen.