Ace in a day

The term "ace in a day" is used to designate a pilot who has shot down five or more airplanes in a single day, based on usual definition of an "ace" as one with five or more aerial victories.

The first aviators to achieve this were pilot Julius Arigi and observer/gunner Johann Lasi of the Austro-Hungarian air force, on 22 August 1916, when they downed five Italian planes.

World War I flying ace Fritz Otto Bernert scored five victories within 20 minutes on April 24, 1917, even though he wore glasses and was effectively one-armed.

A Bristol F2B crew- Canadian pilot Captain Alfred Atkey and English observer Lieutenant Charles Gass- shot down five German planes in a single sortie over Arras on 7th May 1918. Two days later, they were credited with another five enemy machines in the course of two sorties on 9th May. Atkey survived the Great War credited with a total of 38 victories, making him the most successful two-seater pilot of the conflict.

South African pilot Andrew Beauchamp-Proctor of the Royal Air Force flew SE5a fighters with No 84 Squadron and among his 54 victories were five German aircraft shot down on 19 May 1918.

Raymond Collishaw of the British Royal Naval Air Service, piloting a Sopwith Triplane, scored six Albatros D.V fighters near Menen, 6 July 1917.

John Lightfoot Trollope of the Royal Air Force shot down and destroyed seven German planes on 24 March 1918.

Henry Woollett shot down and destroyed six German airplanes on 12 April 1918, setting two afire.

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Wikipedia