This is a French Air Force (Armée de l'Air) Officers Peaked Cap, I cannot say for sure but I believe it to be that of a 2nd Lieutenant (sous-lieutenant), the rank is denoted by the single gold braid around the body of the cap, if this was an Other Ranks cap the chin-strap would be black leather rather than gold braid, and the wings emblem on the cap front would be a plain colour rather than gold
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