Short answer is no, he would have received a different number in the army.
You don't say what the time frame is although if he definitely started in the RAF (and not one of its forebears) it must have been after April 1918? Would you like to post his name and what you know about his place/date of birth and it may be that we can find out something more about him. Does his Long Service and Good Conduct Medal have his number engraved?
MaxD