 He claimed his 90th victory on 31 December 1943 and on 5 February 1944 became the first pilot on the Channel Front to reach 100 victories.Mayer was killed in action on 2 March 1944 while leading an attack on a USAAF bomber formation; he was shot down by P-47 Thunderbolt escort fighters near Montmédy, France.He was posthumously awarded the Knight's Cross of the Iron Cross with Oak Leaves and Swords.