As the Second World War progressed, altitudes got higher, speeds got faster, and temperatures grew colder so warmer clothing was required for pilots and aircrews. Most heavy bombing raids in Europe took place from altitudes of at least 25,000 ft, where it could reach temperatures as cold as minus 50 degrees Celsius. For fighter pilots, the temps grew even colder as they flew higher than the bombers. High casualties over Europe brought bomber air crews new equipment such as the M-3 Flak Helmet, made to fit over the B3 leather helmet, and also a kind of rudimentary early model Flak Vest made by the British Wilkinson Company. With the need and use for such additional amour for flight crews, problems arose on how it was all going to fit on a person. Aircraft were just not insulated against such cold and freezing air so heavy flight clothing was certainly essential. Leather flight jackets such as the A-2, B-3 and G-1 were all functional but the problems of high altitude flight along with the heavy weight and the encumbrance of such thick clothing begged another solution. The need for shearling lined jackets at high altitude was apparent but in the confines of a cockpit or gunning position they proved cumbersome and heavy.
The US Army Air Forces Material Division had been developing a technically modern replacement for the leather clothing since 1942 and the Roughwear Clothing Company of Middletown, PA was selected to manufacture the new B-Series flight jackets in late 1943. Designated No 3157, the B-10 was the first cloth flight jacket to be issued and was designed to be worn with the matching A-9 tousers. With a shell made from a 100% fine cotton twilll, the jackets were lined with Alpaca pile which has incredible insulating qualities and a Mouton sheepskin collar similar to that found on the US Navy G-1 jacket.
The B-10 afforded the wearer all of the warmth found in the older B-3 and B-6 sheepskin jackets but the cotton twill outer meant the jacket was light and flexible, allowing for quick reactions that often meant the difference between life and death. Subsequent development quickly introduced the new Endzone Twill B-15 model, replacing the B-10 and seeing service right through the Korean War in its various modifications. From 1943 to 1945, military and personal photographs of the period show air crews wearing a wide plethora of flight gear and jackets, a mixed bag of issued flight equipment and apparel. Officers of one crew might be wearing an A2 jacket or AN-J-4 Shearling Jacket while several other lower ranks might be wearing an A4 Flight suit with a B-10 or B-15 Jacket worn over it. Several other crew members may have on a B-3 Shearling jacket. The assortment of jackets worn on any one mission by different crew members is astonishing and it seems that keeping warm and functionality was a very personal thing for each crew member.
Post WWII jet aircraft could fly at much higher altitudes and in much colder temperatures than propeller aircraft and were more streamlined in design. Cockpits were cramped and filled with new equipment. Speedy, unimpeded access to and exit from cockpits became even more critical for safety. The B-15