EntityQ3714640· pop 9· linked from 357 articlesO-2Sign in to save1924 observation aircraft family by DouglasConnectionsDouglas mailplaneEntityUnited States Marine CorpsEntityUnited States Army Air CorpsEntityR-1820EntityLiberty L-12EntityUnited StatesCountryMexicoCountryInternational Standard Book NumberEntityunmanned aerial vehicleEntitySecond Sino-Japanese WarEntityUnited States Air ForceEntityChinese Civil WarEntityWacoEntityBoeing B-17 Flying FortressEntityaxleEntityDouglas DC-3EntitybiplaneEntityMQ-9 ReaperEntityDouglas DC-8EntityPredatorEntityCategories1920s United States military reconnaissance aircraftAircraft first flown in 1924Aircraft with fixed conventional landing gearBiplanesDouglas aircraftSingle-engined piston aircraftSingle-engined tractor aircraft