This is an example of a U.S. Army Air Service protective flying helmet worn by the donor during the World War I. While the hard leather exterior did offer greater support than thin-skinned flying helmets, it was lacking in real protection for aviators. The soft cape around the base of the helmet helped reduce the amount of skin exposed to the cold and elements at altitude.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.