"Fatigue was the most universal complaint of pilots. Major Birley attributed its occurrence to the bombardment of the senses by the constant stream of stimuli in the air, many of which were of a peculiar character.⁷⁵ Flyers were observed to stagger from aircraft to make their meticulous reports, which were often a source of conflict as no-one could agree upon what had occurred. Overwhelming tiredness led to frayed tempers and depressed spirits, and the idea uppermost in minds was to lie down and sleep. The repetition of this work over any length of time led to the deterioration of mental and physical wellbeing, inefficiency in the air, and ultimately the shortening of the active service period.⁷⁶ " (Lynsey Shaw Cobden, "The nervous flyer: Nerves, Flying and the First World War," Br. J. Mil. Hist., 4 (2018) 121-142. 

In 1924 Wilfred Trotter(1872-1939) performed the first planned operation for intracranial aneurysm diagnosed pre-operatively.