In Richard E Turner's Book "Mustang Pilot" he says that the Mustang in question was a "war weary" machine that they had modified with the second seat. They used it "Occasionally demostrate tactics to new pilots and give rides to our crew chiefs" They were based at landing strip A-2 on the beachead at Normandy from June 19th 1944. The Eisenhower flight on July 4th 1944 so they could "fly a personal reconnaissance of the Saint-Lo area"