Conversation so far:
When did Chesley Sullenberger get involved with military services?
Sullenberger was appointed to the United States Air Force Academy, entering with the Class of 1973 in June 1969.
Where did he live when he was appointed?
CANNOTANSWER.
How long was he involved in military services?
He advanced to become a flight leader and a training officer, and attained the rank of captain, with experience in Europe, the Pacific, and at Nellis Air Force Base.
Did he advance to any other rankings?
operating as Blue Force Mission Commander in Red Flag Exercises.
When did he operate as Blue Force Mission Commander?
in Red Flag Exercises.
Did he accomplish anything else while in the Military?
While in the Air Force, he was a member of an aircraft accident investigation board.

Question: When did he become a member of an aircraft accident investigation?
Self-contained rewrite: When did  Chesley Sullenberger become a member of an aircraft accident investigation?