OBJECTIVES: Airline passengers are particularly vulnerable to the effects of cardiac arrest due to a lack of access to emergency medical services. To offset this isolation, airlines are installing automated external defibrillators (AEDs) on aircraft. Our objective was to measure the cost-effectiveness of airline AED programs and estimate their value to the flying public. METHODS: A decision analytic model was constructed to estimate the clinical and economic effects of airline AEDs. Inputs were obtained from published data and the FAA. Utility estimates were derived from cardiac arrest survivors. Sensitivity analyses evaluated changes in AED cost and probability of cardiac arrest. Since AEDs may provide utility gains through "peace of mind" for passengers not experiencing a medical event, the impact of this added passenger confidence was also evaluated. RESULTS: AEDs on commercial aircraft cost an incremental $5.16 per flight. AED deployment resulted in an estimated additional $162,000 per QALY gained (16 quality-adjusted minutes per flight). Sensitivity analysis of event probabilities and cost inputs did not substantially change the results. However, the cost effectiveness of AEDs was significantly enhanced by the inclusion of utility gain experienced by passengers from increased peace of mind. While the magnitude of this benefit is unknown, an incremental increase of .003 in utility over the flight duration would reduce the incremental cost-effectiveness of AEDs to less than $50,000 per QALY gained. CONCLUSIONS: Our model estimated that when the benefits of on-board AEDs are limited to patients experiencing medical events, the incremental cost-effectiveness is inferior to most recommended medical interventions. However, if passengers gain utility from knowing an AED is on the aircraft, then these incremental expenditures may be justified. Utility gains from "peace of mind" may have significant implications in determining the value of health care interventions. Further research should be conducted into this potentially important area.