Air leakage measurements by the tracer dilution technique were performed in five military aircraft hangars. The hangars were located in regions of the country having diverse weather characteristics. In several of the hangars, distinct measurements were performed to assess the degree of homogeneity of the air-tracer gas mixture in these large volume structures. Air leakage rates in the range of 0.6 to slightly above 2.0 air changes per hour (ACH)were measured. Surprisingly, these values do not differ significantly from those which might be measured in single-family residences.