This is my current "penciled" in thoughts that I use to guide me. The Germans will be roughly a generation or a "half" generation ahead with certain countries on par or ahead in their "niche."
For example the British have an obvious need for longer ranged heavier bombers so that will get their focus, same with interceptors and radar for defense. The RAF as formed will let Army co-operation, ground attack and naval air suffer. They will be biased that "the bomber always gets through" and the fact that the enemy is "over there." German has its feet in everything but its priority will be air superiority and as they understand the RAF threat it will follow with interceptors and radar. Ground attack and medium bombers get priority to support Army operations. The Navy will be more independent longer and develop longer ranged aircraft, this will translate to heavy bombers once (or if) the Germans view Britain as a threat. The French should focus on fighters and radar then medium bombers and lastly heavy bombers. Russia should dominate German planning so I think the aircraft designed and built look to fighting them.
I think an issue will be overflight rights with less openness through the 1920s and 1930s at least. Civil aviation may get more restricted as a London to Berlin flight may not happen, instead you fly British to Amsterdam then German to Berlin or if lucky KLM all the way. Germany might be forced to use Zeppelins to overfly water only routes between Berlin/Hamburg/or Frankfurt and NYC. A lot of convoluted routing to avoid "hostile" airspace. Imagine if Italy refused to let British or French overflights? Or if Germany was denied flying over UK and France? I think that favors Zeppelins for Germany and also bigger flying boats as well as longer ranged aircraft generally. That may tie in with a less robust land (paved) airport infrastructure without another war too.
I would predict that Germany is a leader in civil aviation, not fully dominant but definitely having a big share. It should build and operate Zeppelins to cross long distances and pursue longer ranged aircraft also but the USA will lead the latter, buy the former and Britain will be a competitor. Both Britain and the USA should be leaders in large flying boats for civil aviation and that is how they compete with Zeppelins. Thus I think you get aircraft like the Constellation built in America as it has the distances over land to spur development, the flying boats serve longer on over water international routes except Europe to America where Zeppelins skim off mail and luxury passengers, the fixed wing and flying boats dog them until they get the upper hand by the late 1940s. Germany and the British likely are early innovators in jets and the USA should not be far behind, but I would give the Germans the edge in putting advanced ideas into production faster through the 1950s when things should get more even. That should give the Germans an edge in transport aircraft but the USA and UK have greater need for big air cargo lifters with range than does Germany so I think the Germans build great medium planes with the USA or UK leading in the big ones (think C130 vs C141). I think the Germans lead in military aircraft design but the USA will be dominant in Naval aircraft for many years. The British need the Navy to get back in control of the Fleet Air Arm before they can close the gaps. The USA will export more as the military should remain smallish.
The biggest change I made was having the USA neutral and I am pondering having the UK neutral as well. With a neutral USA their is greater room for a geopolitical shift with fertile ground for American-German cooperation. Both are going to have strong civil aviation industries and little conflict so I see more sales of German hardware, joint ventures and cross-pollination generally. For example Fokker returns to the Netherlands due to a tax problem, he is still a supplier to Germany as the trade relations between the Dutch and Germans should be very strong, Fokker went to the USA and he became involved with North American (a GM company then). GM owns Opel. Ford too might partner as did Goodyear with Zeppelin to keep in the aviation business. Overall I think you see a certain globalization of aviation sooner. Here the Anglo-French should track faster into their relationships. By the 1970s I see the biggest aerospace firms jointly American-German and Anglo-French. Imagine the Concorde program competing with a Junkers/Boeing or Folke-Wulf/Lockheed team.
I have kept the basic Army (Air Force) and Navy duality in Germany, unlike the unified RAF, so things look like how the USA was bifurcated but I think a unified Air Ministry does develop, that may hinder things until civil aviation moves to Transport and the unified Defense Ministry works out how best to oversee aviation and electronics development. I see the Deutsche Luftstreitkräfte staying aligned to the Army just like the Army Air Corps (Force) rather than going independent like the RAF. Eventually it becomes a separate force the way the Army, Navy and Luftwaffe were "unified" in the Wehrmacht. I have washed Luftwaffe from the vocabulary and I allow for some infighting but nothing like the Goring vanity show. In fact I tend to think there will be two camps, Army and Navy Air, with several unions, Fighters, Bombers, Ship-board, Maritime Patrol, Bombardment, Attack, etc., these will all compete for funding like the real world and pull for their own planes and style but cooperate on common ground. A long range maritime patrol plane is similar to a long range bomber for example so the contractors will be finding cross over applications for both engineering and aircraft. Overall I think we see at least 5 years if not 10 shaved off many developments, more if we also butterfly away the Depression.