These were part of the USAF’s flight clothing system, often layered under leather flight jackets like the A-2 or with other cold-weather gear e. Key Details from Your Photos: Label: Clearly reads SHIRT, FLYING, HEAVY / TYPE A-1A / SPEC. MIL-S-6282 / SIZE LARGE / LION UNIFORM COMPANY / U. This matches known examples from the period. Design: Dark blue (a common USAF shade for these), four button-flap cargo pockets, button-front closure, spread collar, adjustable button cuffs, and a tailored fit for wear in aircraft. Material: Heavy wool (often described as blanket-like weight for insulation). Measurements (from your tape): Length (collar to hem): 29 inches. Sleeve: 22-23 inches (typical for Large). It’s a boxy, utilitarian military cut. These shirts were produced by contractors like Lion Uniform Co. The blue version is distinctive to the post-1947 independent Air Force (earlier WWII-era ones were often brown/OD wool). They saw use into the 1950s-60s before being phased out with newer synthetic and Nomex flight gear. Today, they’re popular vintage military collectibles, often worn as rugged overshirts or jackets. Yours looks to be in decent condition with the classic “US Property” marking.