Air travel exposes patients with chronic obstructive pulmonary disease to the risk of severe hypoxemia. We sought to determine the frequency and outcome of airline travel in patients with chronic obstructive pulmonary disease. A cohort of 100 patients (76 men and 24 women; age 67 +/- 7 years [mean +/- SD]) with severe chronic pulmonary obstructive disease examined by means of spirometry (forced expiratory volume in the first second, 0.04 +/- 0.35 L), all military retirees, or their dependents, comprised the study population. Forty-four patients traveled by commercial air carrier over a 28-month interval, giving an annual frequency of 18.9% of these patients per year. The group that did not travel by air (n = 56) had a lower mean value for forced expiratory volume in the first second and greater prevalence of home oxygen use than did the group that did travel by air. Twelve of the travelers (27.3%) consulted a physician beforehand. Flights reached foreign destinations for 22.7% of patients. The median duration of the longest flight segment was 3 hours. A minority of patients (34.3%) occupied seats in the smoking sections of aircraft. A majority (56.8%) ambulated aboard the aircraft during flights. Eight patients (18.2%) reported transient symptoms during air travel. We conclude that patients with chronic obstructive pulmonary disease travel with appreciable frequency, often without medical consultation, and develop symptoms in some cases.