A single-pilot form of the line operations safety audit was trialed with a mid-sized emergency medical service air operator using two observers with a sample of pilots flying 14 sectors. The conceptual basis for observing pilot performance and analyzing data was the threat and error management model, focusing on threats, errors, undesired aircraft states, and their management. Forty-six threats and 42 crew errors were observed. Pilots generally used sound strategies to prevent errors and to manage successfully those that occurred. Threats resulting from operational pressures were well managed. The study achieved its objective of determining whether a single-pilot line operations safety audit could be successfully developed and used as a basis for systematic data collection.