You have been requested to volunteer yourself and your civilian P-51D mustang for a top secret mission. More details to come once you're airborne. Playthrough of the mission: https://youtu.be/G8FRWWdyCZg
There have been some rumors amassing about strange vehicles and soldiers collecting at one of the shipping ports in the area. You've been issued a formal request from what appears to be a government agency of some kind to provide assistance. They will need you as a pilot and your civilian P-51D mustang. More details about what is going on will be given once you're in the air and en route.