Technically the RAF did not exist during WW!
The RAF was founded on 1st April 1918 under the control of the British Government Air Ministry, making it the oldest independent air force. This brought together the Royal Flying Corps, who had been under the control of the British Army, and the Royal Naval Air Service, previously controlled by the Admiralty.
So you should be asking about the Royal Flying Corps or the RNAS, if you know which arm is appropriate for your profile.