Contrary to some misconceptions, the Luftwaffe did not deploy Romanian, Hungarian, or Bulgarian pilots or aircraft during the Battle of Britain (July–October 1940) nor in the defense of France and the Low Countries earlier that year. The German air force relied exclusively on German personnel and domestically produced aircraft—primarily Messerschmitt Bf 109 and Bf 110 fighters, along with Heinkel He 111, Dornier Do 17, and Junkers Ju 88 bombers—during these critical early campaigns.
While Germany's Axis allies did contribute air forces to the Eastern Front later in the war (notably Romanian and Hungarian units supporting Operation Barbarossa from 1941 onward), they were not integrated into Luftwaffe operations over Western Europe during 1940. The Battle of Britain was a distinctly German-versus-British aerial conflict, with the RAF's Fighter Command facing the Luftwaffe in a struggle for air superiority that ultimately thwarted Hitler's invasion plans.
This distinction matters historically: the Battle of Britain was the first major military campaign fought entirely by air forces, and its outcome hinged on British radar, command systems, and pilot resilience against a purely German aerial onslaught.