A man or woman's closet must still have an aviator jacket, the epitome of timeless and classic fashion. This clothing was originally designed to shield Air Force personnel from the chill in the cockpit. They decide to utilize leather as their main material for this reason. In addition, leather's timeless classic design makes it possible to provide superior insulation at a lower cost. But as technology advanced, altitude rose, and sheepskin replaced the lining to more effectively trap interior heat.