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 Chesley Sullenberger live when he was appointed to the Air Force Academy?
How long was Chesley Sullenberger involved in military services?
After 30 years with US Airways and its predecessor, Chesley Sullenberger retired in 2010.
Did Chesley Sullenberger advance to any other rankings, besides captain?
Chesley Sullenberger advanced to become a flight leader and a training officer, as well as operating as Blue Force Mission Commander in Red Flag Exercises.
When did Chesley Sullenberger operate as Blue Force Mission Commander?
Did Chesley Sullenberger accomplish anything else while in the Military besides advance to become a flight leader and a training officer, as well as operating as Blue Force Mission Commander in Red Flag Exercises?
While in the Air Force, Chesley Sullenberger 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?