Mayer, nicknamed Mayer-Ast,[1] was born on 9 March 1911 in Rufach at the time in the Imperial Territory of Alsace–Lorraine as part of the German Empire, present-day Rouffach in north-eastern France.

[4] On 7 February 1938, Mayer claimed his first two aerial victories when he shot down a Tupolev SB bomber and a Polikarpov I-16 fighter.

[7] World War II in Europe began on Friday 1 September 1939 when German forces invaded Poland.

[8][9] He claimed his first victory of World War II on 5 November 1939 downing a French Potez 63 reconnaissance aircraft near Saarburg.

[12] Mayer claimed eight more victories during the Battle of France, including five aircraft shot down on 14 May 1940, making him an "ace-in-a-day".

On 25 August, Mayer shot down a Hurricane for his 15th victory, possibly that of Flight Lieutenant Alfred Bayne of No.

[14] Alternatively, according to military aviation historians Christopher Shores and Clive Williams, his victim may have been Pilot Officer Jacques Philippart who bailed out and came down in the English Channel and subsequently died.

[17] Mayer was made Gruppenkommandeur (group commander) I. Gruppe of JG 53 on 1 September 1940, he replaced Hauptmann Albert Blumensaat who was transferred.

On 17 October 1940, Mayer took off in Bf 109 E-7 (Werknummer 4138—factory number) on a test flight and never returned, his body washing up on the English coast 10 days later.