A passenger comfort survey was conducted with a major U. S. airline with the objectives to determine: 1) the variables that affect passenger comfort, including air quality variables; 2) the level of passenger comfort during flight and whether passengers are experiencing specific types of health-related symptoms; 3) if passenger comfort is a function of the percent of bleed air vs. filtered, recirculated air, standard-body vs. wide-body aircraft, and flight length. Flight attendants distributed the self-administered questionnaires as part of their normal duty. Data from 3630 passengers on 71flights were collected in March, April, and June 1997. The response rate was approximately 43 percent. Conclusions from the study were that seat comfort, flight smoothness, and air quality were the important determinants of passenger comfort. The most frequent symptoms experienced by passengers included back/joint/muscle pain, dry/irritated/itchy eyes and dry/stuffy nose. These symptoms increased with flight length. On longer flights, seat discomfort became noticeable to passengers before eye and nasal symptoms. The percent of filtered recirculated air showed no direct relationship to passenger comfort ratings or reported symptoms.