Methods, systems, and apparatus, including computer programs encoded on computer storage media, for unmanned aerial vehicle authorization and geofence envelope determination. One of the methods includes maintaining, in a datastore, flight operation information associated with UAV flight operations. A request to generate a risk assessment report is received, with the request including aspects of a UAV flight operation, with the risk assessment report describing risk associated with each aspect. Flight operation information accessed from the datastore is analyzed. Performance characteristics are determined based at least in part on the analysis of the flight operation information, with the performance characteristics including information that can inform, or affect, a safe or functional UAV flight operation. Risk assessments for each aspects in the request are determined using the performance characteristics. The risk assessment report is generated using the determined risk assessments.