Passengers' comfort is becoming more and more important in aircraft cabins. In this study, thermal environment parameters on 10 airlines (1 international and 9 domestic) including 23 aircrafts and 6 different aircraft types were measured with 155 subjective questionnaires regarding passengers' comfort collected. Thermal environment parameters contained air temperature and relative humidity, wall temperature, radiant temperature, air velocity, noise, illumination, and absolute pressure. The questionnaires collected basic information of passengers (age, height, weight, and clothes level) and their evaluation of the environment (thermal comfort, perceived air quality, and symptoms). The results showed that air temperature was between 23 and 27 degrees C and average level of humidity was 26.3 %. Wall temperature was slightly lower than air temperature, but radiant temperature was very close. Air velocity was generally below 0.2 m/s, which was imperceptible for passengers. Average noise level was 82.5 dB (A weighted sound pressure level). The illumination changed greatly, and air pressure dropped when taking off and rose when landing and at cruise period; low pressure between 77 and 90 kPa was maintained. Subjective questionnaire assessment showed passengers were satisfied with the environment, and they believed noise and air pressure contributed most to their comfort level. More than 15 % of the passengers reported drowsiness and symptoms related to humidity (dry eye, nose, and throat). Deep analysis indicated that the longer the fight, the less comfortable passengers felt. Seasonal factor showed no significant influence on comfort level.
