Donaldson graduated from the Navy's Postgraduate Aviation Safety School in Monterey, California, where he completed the long course in aviation safety and crash investigation. He served as a safety officer and crash investigator at both the Squadron and Air Wing levels, and was qualified as a maintenance check pilot in six models of prop and jet aircraft. Also, he was a qualified air traffic controller and served for two years as a Carrier Controlled Approach Officer.
After his retirement, he conducted an independent investigation of TWA flight 800, concluding it was shot down by a missile, probably shoulder fired.
William Donaldson died of a brain tumor at the age of 56.