July 13, 1918 postage rate reduction cover. The air mail rate was reduced from 24 cents to 16 cents July 15th 1918. Cover only flown on the 15th as it has a New York July 15th back stamp. "National Aerial Coast Patrol Commission" corner card & sent to the "Aerial League of America". Some vertical creases at left. Catalogues US$800.00 in Scott..