I did a quick military search. 458 Service Records on the info. you gave me. No Alexander Kendall. 215 Pension Records. No pension records. There was nothing for the Royal Flying Corps.
There are other records and I suggest you do a military search and type in his name and under military. Put in WW1. Under "Keyword". Put in Royal Flying Corps. You will have a lot of info come up.
You may do a general search and under Keyword put in "Royal Flying Corps;, but under all the info. Put in as much info as you know about him. Birth, Father, mother, spouse, & children. Where he might have lived at.
If you have any idea where he was born at and grew up at. That is where he most likely enlisted from. Especially if he went in as a young man. He might have lied about his age and went in as a very young man. Good luck.