Herrington received his commission in the U.S. Navy from the Aviation Officer Candidate School at Naval Air Station Pensacola, Florida in March 1984. In March 1985 he was designated a Naval Aviator and proceeded to Patrol Squadron Thirty-One (VP-31) at Moffett Field, California for training in the P-3C Orion. His first operational assignment was with Patrol Squadron Forty-Eight (VP-48) where he made three operational deployments, two to the Northern Pacific-based from Naval Air Facility Adak, Alaska and one to the Western Pacific-based from the Naval Air Station Cubi Point, Philippines. While assigned to VP-48, Herrington was designated a Patrol Plane Commander, Mission Commander, and Patrol Plane Instructor Pilot.