Luftwaffe Flight Cap

A Luftwaffe navigator checks his course while laying in the nose of his Heinkel He 111 medium bomber. He is wearing a fliegerkopfhaube (flight cap). During World War I, most pilots quickly realized the need for protective headgear due to the cold weather effects while in an open cockpit.  As no headgear was readily available, pilots were forced to utilize commercially produced leather motorcycle and automobile helmets.  During World War II, the German military produced approximately 10 variations of flight helmets for various operational conditions, as well as with or without radio communication equipment.  This specific helmet was designed with radio equipment for fighter and bomber pilots.  It was similar to the earlier model used in the early months of the Battle of Britain (LWpW100), however with updated features.

Source :
https://www.angelfire.com/on4/okw/luftwaffe2.htm
https://axis-militaria.com/product/ww-ii-german-aircraft-lkpw101-fliegerkopfhaube-winter-flight-cap-nice/