Aerial aeroplane Air Racer air-to-air aircraft airplane Aviation Keith 'Frosty' Frost military N2269U North American Aviation AT-6 Texan Yale SNJ Wirraway Harvard North American Aviation SNJ-4 ocean radial piston engine radial-engine retractable gear single-engine tail-dragger trainer United States Army Air Corps USAAC United States of America warbird World War II WWII