That's a good idea. Haven't done it much myself but music can be important addition, especially played on separate portable system to keep your computer resources free for Aces High.
Prefer marches myself, and be sure to add the many excellent UK pieces like Colonel Bogey and Scotland the Brave.
Favorite U.S. marches that come to mind include American Patrol, When Johnny Comes Marching Home, Grandioso, Guadalcanal March from Victory at Sea, Semper Fidelis, U.S. Field Artillery (the Army anthem Caissons Go Rolling Along), and all the U.S. military service anthems like Wild Blue Yonder, Anchors Aweigh and Marine Hymn.
German music would have to include Old Comrades.
Russian music naturally would include Meadowlands.
If we ever get a French aircraft, try Sambre et Meuse. And Algerian Suite's French Military March (after WWII, but close enough).
Plenty of wonderful Italian music, but offhand can't think of most appropriate for Aces High. Ditto for our Brazilian P-47.