The rules state that you look up the results in the table, but not what the results mean?
In all cases, the unit leaves the game. We'll delete the words "attempt to" in the first sentence of 12.1 to avoid confusion. "Damaged" and "Destroyed" are per 9.3.1-2. "Safe Escape" means the aircraft's condition does not change.
must both aircraft in a unit disengage?
Yes. 12.1 says, "You may attempt to remove your Element from combat through Voluntary Disengagement" [emphasis added] and "If you have a Wingman, repeat this procedure for him."