Germans flying hugely inferior planes
The Bf-109 wasn't really inferior to the Spitfire, but it was an equal. However, for the purposes of the British in the Battle of Britain, equal was enough since it was the first the Germans had encountered a fighter of roughly equal quality to the Bf-109 in large numbers. It had been superior to anything it met over Poland in 1939, and virtually all the fighters it encountered over France 1940, with the exception of the French D.520, which was encountered in minuscule numbers. The Spitfire of May and June of 1940 was equipped with a fixed pitch propeller which gimped it significantly in combat. German 109 ace and leading fighter tactician Werner Moelders tested a captured Spitfire I after the Battle of France and praised its handling characteristics, but stated "as a fighting aircraft, it is miserable." He was unpleasantly surprised by the upgraded Spitfires the
Jagdwaffe ran into during the Battle of Britain only a month later, which were now equipped with a variable pitch propeller and were flying on 100 octane fuel. This was the first time the Luftwaffe's 109 pilots met an adversary in a plane that was their equal, and it led them to obsessive levels of worry, with every cloud hiding a lurking Spitfire.
Nevertheless, the German pilots still had the advantage of superior fighter tactics for most of the Battle, flying in the far superior four plane
schwarm formation, compared to the rigid three plane "Vic" formations still drummed into the heads of new recruits by the RAF training establishment. Historian Stephen Bungay estimates that German 109 pilots, despite fighting the RAF on its home ground and directed by the advantage of radar, still scored a positive K/D ratio of around 1.2:1 (although the RAF fighters more than made up the difference against German bombers, allowing them an overall K/D of 1.8:1) Some RAF squadrons ditched the vic once they gained combat experience, however they still had to fish around for their own solutions, many of which were halfway stopgaps. It wasn't until early 1941 before Fighter Command finally officially adopted the
schwarm as the "finger four."
After the Battle of Britain and their nasty brush with the Spitfire, the German 109 pilots went back to facing fighters with varying degrees of inferiority. The Red Air Force of 1941 could not match the
Luftwaffe for quality in tactics or machines, while in the deserts of North Africa the newly arriving Bf 109F encountered the Hurricane and the P-40 in numbers, both of which it had a clear edge over. In the desert allied fighters were also tied to operations that placed them at a disadvantage, and German ace Hans Joachim Marseille scored many of his kills against Hurricanes and Warhawks caught at low altitude and laden for ground attack.
And then in the Summer of 1941, as Fighter Command's Spitfire Vs were conducting their sweeps over France, they started to encounter the FW 190A - the "butcher bird." The Focke Wulfe could not turn anywhere near as quickly as the Spitfire, but it was far faster, with incomparably superior roll at combat speeds allowing for rapid changes of direction. The margin of superiority was so vast the 190 quickly established a 5-1 kill ratio, and the season became known to the outclassed pilots of the RAF as the "Focke Wulf Summer," which would only end in July of 1942 with the hurried introduction of the Spitfire IX.
By then the tide was starting to turn against the Luftwaffe. The latest 109 variant, the "Gustav," was a disappointment after the superlative "Freidrich," while Allied aircraft were continually improving in quality. The Americans were starting to arrive, while perhaps just as dangerously the Red Air Force had recovered, and with its increasingly confident fighter regiments equipped with new Yakolevs and Lavochkins, was able to contest German air superiority. On all fronts the Germans now had to fight planes that matched or even exceeded their own in quality
as well as quantity. The Germans would be on the back foot in the air for the rest of the war, and their attempt to change the game with the Me 262 came too late and in too small numbers to make an impact.