No, it is not a Nazi symbol.

In WW I it was used as military insignia on airplanes, tanks and other vehicles.
(https://en.wikipedia.org/wiki/Luftstreitkr%C3%A4fte)

It was not used as military insignia in WW II. The insignia of the “Wehrmacht” (German Armed Forces) has been another kind of cross: the straight-armed “Balkenkreuz” (beam-cross).
(https://en.wikipedia.org/wiki/Wehrmacht)

But as a decoration medal this Shape was used in both World Wars as “Eisernes Kreuz Orden” (iron cross medal). (https://en.wikipedia.org/wiki/Iron_Cross)

Nowadays a more modern designed, but still quite similar shape of the cross is used as military insignia by the “Bundeswehr” (German Federal Armed Forces).
(https://en.wikipedia.org/wiki/Cross_patt%C3%A9e)

I may be misunderstanding what this symbol is, but isn't it the German Iron Cross used in both World Wars on German Nazi vehicles as a since of pride and identification of German artillery?

Ich liebe! Would fly with pride.

Ave Maria! Deus Vult!

@ Allons:
Generally I think, there is no correct name ore incorrect name of a decal. There is just a given name from the creator.

But you are right. The geometrical form of this cross is called "cross pattée" (or in german "Tatzenkreuz").

In its use as a heraldic symbol, military emblem or military decoration it is also called "Iron Cross" ("Eisernes Kreuz") or "Black Cross" ("Schwarzes Kreuz"). The "Knight's Cross" ("Ritterkreuz") or let's take the exact phrase "Knight's Cross of the Iron Cross" ("Ritterkreuz des Eisernen Kreuzes") is a special higher class of the military Iron Cross decoration.

Well, inspired by your correction I will rename my decal. Correct or not, it is no longer called "Knight's Cross" ("Ritterkreuz"), now it has the more poetical phrase "Cross of the Airborne Knights" ("Kreuz der Ritter der Lüfte"). ; )

@A_Harmless_Fly:
Thanks for this useful hint! Now I got the recommended informations and I will redesign the decal soon.

Ritterkreuz is not the correct name of this type of cross, better use "cross patty" see https://en.wikipedia.org/wiki/Cross_patt%C3%A9e

read the requiremnts another time and repost if you want a chance, the translucency.

DEUS VULT