The aim of this study was to compare the impact of different flight path models on the calculated population coverage of aeromedical retrieval systems, using the state of Alabama as a case study. Geospatial analysis of U.S. Census Bureau population data using helicopter bases and trauma centers as foci of either circular or elliptical coverage areas. Circular isochrone models around helicopter bases or trauma centers suggest that the entire population of Alabama could reach a level I or II trauma center within 60 min. Elliptical isochrones, incorporating outbound and inbound flights, suggest that only 78.8% of the population have ready access to level I or II trauma centers. While all three flight path models described have some validity and utility, simplistic circular flight time isochrones around trauma centers and helicopter bases provide overly optimistic estimates of population coverage. The elliptical model provides a more realistic evaluation. •Accessibility of trauma services is often measured in terms of population coverage.•This study shows that the flight path model has a major impact on population coverage.•Simple models suggest 100% of Alabama residents have access to trauma care by air.•More complex models suggest that only around three-quarters of residents have access.•Harmonizing the reporting of air medical system coverage should be considered. Simplistic circular flight time isochrones around trauma centers and helicopter bases provide overly optimistic estimates of population coverage. Using the ellipse model, including allowance for mission ground time, provides a more realistic assessment.