I knew it was used by the Finnish airforce during ww2:

And this is the story behind it:

The Swedish count Eric von Rosen gave the Finnish White government a Thulin Typ D aircraft.[...]

Von Rosen had painted his personal good luck charm on the Thulin Typ D aircraft, which was a blue swastika. This was to become the insignia of the Finnish Air Force. The white circular background was created when the Finns tried to paint over the Thulin air academy advertisement.[3] The swastika was officially taken into use after an order by Mannerheim on March 18, 1918. The FAF had to change the swastika insignia after 1945, due to an allied control commission decree, where all swastikas had to be abandoned. However, the original swastika can still be found in regimental flags and medals, especially in the air force.

wikipedia of course

So it predated the German one. Swastikas was just one of those things that were popular during that period.

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