The children were forbidden to ask him, and punished if they did, but the medals and commendations from this one mission were tucked away in a drawer. This was my friends understanding of this mission. Just wondering if there is a historical mission that matches this description. My recollection is that he flew B-24's.
What your friend is describing, from what I can tell, sounds essentially like Operation Vengeance, the April 1943 mission to hunt down and kill Japanese admiral Isoroku Yamamoto, the commander-in-chief of the Imperial Japanese Navy's Combined Fleet and planner of the Pearl Harbor attacks, as well as other members of his staff. Japanese coded messages had been intercepted, and Yamamoto's itinerary through the Solomon Islands was known.
The P-38s so used to shoot down Yamamoto's plane were equipped with one 330-gallon and one 165-gallon drop tank, to provide enough fuel to complete the mission successfully. Both of the planes carrying Yamamoto's party were confirmed destroyed (the six A6M Zeros escorting Yamamoto were also engaged, but none were claimed), and one P-38 and its pilot (of the sixteen sent) failed to return.