Jack McCleery was born in Belfast in 1898, the son of a mill owning family. He joined the RNAS in 1916 as a Probationary Flight Officer. During the next ten months he completed his training at Crystal Palace, Eastchurch, Cranwell, Frieston, Calshot and Isle of Grain, flying more than a dozen landplanes, seaplanes and flying boats, gaining his wings as a Flight Sub-Lieutenant.