Data analysis Tracheal tube cuff pressures will be analyzed and reported as continuous variables. The presence of tracheal tube cuff pressures exceeding 30 cm H2O is a dichotomous outcome and reported as a proportion of those exceeding this threshold. Differences in mean change in tracheal tube cuff pressures between study groups (air or saline) within each aircraft type (rotor or fixed wing) will be reported as mean + standard deviation, and compared using the unpaired t test, with p<0.05 considered as significant. The relationship and strength of association between tracheal tube cuff pressures and altitude will be analyzed by regression by least squares methods and Pearson's correlation coefficient, respectively. The incidence of adverse events due to tracheal tube cuffs, including those due to use of saline in cuffs, will be reported using descriptive statistics. Differences in adverse events between study groups (air or saline) within each aircraft type (rotor or fixed wing) will be compared using the unpaired t test. Results are reported as mean + standard deviation, with p<0.05 considered as significant.