Aerial overview surveys are carried out by observers in fixed-wing aircraft flying at appropriate safe heights above ground level over the forest canopy. Surveys cover extensive areas to detect as many new FHDA-caused disturbances as possible. Surveyors record locations, extent, severity, possible causative agent and host tree species involved in the disturbances. Aerial surveys are cost-effective means of obtaining forest health damaging agent (FHDA) caused disturbance data at the landscape level. These surveys help to manage forests by providing early detection of FHDAs and once detected, by monitoring their trends. Aerial surveys are carried out to record locations, extent and severity of new, FHDA-caused disturbances. changes to known FHDA disturbances for historical and evaluation purposes. background information needed for planning management actions. and, forest health data at the forest area, regional and provincial levels for reporting and inventory update. This dataset contains data from 1975 to 2010. Data from 2011 onward is available as a separate dataset.