An assessment of aerial firefighting response times between agencies during the 2020 fire season in California

Rapid, well-coordinated aerial response can limit wildfire growth during the initial response (IR) period. Most quantitative studies of wildland fire aviation effectiveness have relied on aircraft data from the United States Forest Service (USFS), with comparatively less attention to other agencies. This study leverages open ADS-B data to reconstruct second-by-second aircraft movements for both the California Department of Forestry and Fire Protection (CAL FIRE) and USFS fleets during the 2020 California fire season, enabling the first direct cross-agency comparison of operational use. We characterize fleet activity patterns and evaluate how landscape, weather, and values at risk influence time to first aircraft arrival within 24 hours of ignition. ADS-B flight tracks were matched to 7,214 wildfires; response time was defined as the interval between ignition discovery and the first ADS-B detection within 5 km. Cause-specific cumulative incidence curves compared the probability that each agency arrived first. Cox proportional hazards models, stratified by diurnal period and protecting agency, quantified the effects of slope, fuel moisture, temperature, distance to water, and human exposure metrics on dispatch timing. Aircraft responded to 1,476 fires, with USFS aircraft exhibiting slightly shorter mean response times. Hazard ratios indicated faster response under higher temperatures and closer proximity to populated areas, whereas wetter fuels and greener-than-average vegetation were associated with delayed arrival. These results demonstrate the feasibility of near–real-time, cross-agency performance monitoring to inform resource allocation and support integration of ADS-B data with federal tracking systems for enhanced aviation situational awareness.