IMHO there was at that time (WW-I) no braver group of people than those who flew those wood and silk death-traps known as aero-planes. The engines could barely get the plane into the air. The pilot sat with no parachute on a piece of 3/4” plywood behind a fuel tank that was not self-sealing and would explode if exposed to any type of spark. There was no protection for the pilot from the weather or bullets or anything else that happened to occupy the same airspace at any given moment. Yet many men took to the air every day knowing that fewer would come home later.
That is the very definition of brass balls.
Many preferred that to the trenches. Shows how bad the trenches were!