The specifications for the U.S. Army Air Corps Type A-2 jacket (regulation summer flying jacket), adopted in 1931 and the most familiar among all leatherflight jackets, stated that it should be made of horsehide tanned to seal brown. However, initially, oxidation during the dyeing process caused the jackets to end up russet (a lighter, reddish brown) in color. Later in the decade, they were able to prevent oxidation during dyeing, and the jackets produced were a proper stone brown.