Already a famous actor by the 1930′s, James Stewart, who had his commercial pilots license, enlisted in the Army Air Corps at the outbreak of World War Two. Due to his celebrity status, the U.S. Army relegated Stewart to instructor duty and recruiting roles, much to his dismay. After repeated requests for combat duty, Stewart was sent to A B-24 Liberator unit in the 8th Air Force, where he flew 20 combat missions over occupied Europe.
After the war, Stewart transitioned to the USAF and attained the rank of Brigadier General in the reserves. During Vietnam, he flew as an observer on a B-52 Stratofortress bombing mission during Operation Arc Light. Stewart refused to let the mission be used for publicity, saying that he was only doing his duty.
I can’t imagine any modern day hollywood type doing anything like this.