An aviator hat, also known as a bomber hat, is a usually a leather cap with large earflaps, a chin strap, and often a short bill that is commonly turned up at the front to show the lining (often fleece or fur). It is often worn with goggles. It may be made of other materials, such as felt.
In the first days of aviation, the leather helmets used in motor-racing were adopted by pilots as head protection. During World War I, British Engineers led by Charles Edmon Prince added earphones (now called headphones) and a throat microphone to make a "hands-free" communications systems for Flight Helmets – then called "aircraft telephones". The Group's first product was a hand held "aircraft telephone" and, over a 3 year-process of experimenting with various voice microphones, found the hands-free throat microphone built inside a flight helmet much more user-friendly in open-cockpit airplanes due to excessive wind noise and vibrations.
The initial design of early leather flying helmets was adapted during the 1930s to become the iconic type B helmet which enabled the external attachment of radio earphones, oxygen masks, and removable goggles to protect pilot's eyes from the elements. A detailed description of a typical Type B helmet can be found on the website of the Imperial War Museum (London, England). It is made from six vertical panels which meet at a central ridge panel running from front to back. There is a rectangular horizontal panel which goes across the forehead and it includes padded leather oval housings at the ears. The chinstrap, also made of leather, is stitched to the right side and buckled to a small strap on the left. The brown leather of the helmet is lined with buff-colored chamois and has a rectangular length of brown-colored material sewn to the inside of the forehead.
With the advent of closed-cockpit airplanes, hats became less necessary (Charles Lindbergh still wore one when he crossed the Atlantic in 1927, though his Spirit of St. Louis monoplane had a closed cockpit). Nonetheless, aviator's hats continued in popularity as a fashion accessory and winter hat. Aviator's hats continued in aviation use through the Second World War, until the age of jet fighters, when solid plastic and, later, carbon fiber helmets replaced leather caps in the cockpits of planes.