=+11.45 Some commercial airplanes recirculate approximately 50% of the cabin air in order to increase fuel efficiency. The authors of the paper “Aircraft Cabin Air Recirculation and Symptoms of the Common Cold” (Journal of the American Medical Association [2002]: 483–486) studied 1100 airline passengers who flew from San Francisco to Denver between January and April 1999. Some passengers traveled on airplanes that recirculated air and others traveled on planes that did not recirculate air. Of the 517 passengers who flew on planes that did not recirculate air, 108 mptoms, while 111 of the recirculate air reported evidence to conclude that post-flight respiratory o and do not recirculate s using a 5 .05. You may