A lot of the comments understate the German problem and the scale of solution needed and the way Germany fights the war, what they do is a feature not a bug.
Just to scale things the Kreipe Korster study gives the LW aircrew production 1 sept – june 44 as 29k personnel. The Commonwealth air training programme alone is designed in December 39 to produce 50,000 aircrew a year.
The Army is geared for fast violent decisive campaigns lasting around 2 months max its perfectly acceptable to push everything into winning the campaign decisively and then rebuild. After all you are losing 20-50% of the front line aircraft strength during the campaign anyway.
The Luftwaffe staff recommendation was actually to reduce the size of the air force by 20-30% in order to ensure adequate reserves of aircraft.
The Luftwaffe command solution was to maximise front line strength when you needed it. And that means at every pre war crisis you end up suspending training and suspending the expansion of training and not so incidentally intimidating France. Once you go to war its maximise everything.
Germany has a very thin technical skills base. Immediately pre war they are running into skill shortages in the aircraft industry capping off production. Those shortages will extend to maintenance crews in the service. This is not surprising, they go from nothing to 10,000 a/c pa in around 7 years.
The same issue applies to the Heer. Its mobile units have around a 6-week full strength life. After around 6 weeks the forward maintenance organisation rapidly collapses until units are around 50% vehicle strength and they stay there until they get to stand down. This is just mechanical issues not enemy action.
Changing that requires an increase not just in aircraft and IP but also in the base personnel to service them and the training establishment to produce them in the first place and that comes at a cost in something else. Basically the army. That's counterproductive, reducing the scale of the army especially the motorisation runs entirely counter to the concept of warfare intended to avoid a war of attrition against an economically superior enemy.
Come wartime there is a massive expansion from summer 39 – just before the BoF the LW increases flight schools by 42% and aircrew to 4700 ( up 31%) with 3,900 first line aircraft available for the BoF. But they also lose about 1000 kia and 700 wia in training accidents to achieve this. Thats a large proportion of the annual production of training aircraft btw.
As long as you as you win what’s the problem? You can win, then stand down and replace at comparative leisure.
That changes for the LW in 1940 when they get stuck in a long war Vs the RAF, but its manageable. The LW can decline battle any time it chooses, the RAF is not hitting anything vital. But it does not change for either the Heer or Germany. They can still win wars in short campaigns and are gearing up for the 6 week campaign to destroy Russia and get the resources needed for long war.
Sometime between late 41 and mid – late 42 it becomes a problem the LW cannot manage, some units are losing 100% of aircrew every three months, but by then you are playing catch up with much larger technical and economic powers who intended to fight a long war from the start and you are going through your entire front line strength about every 9 months.