sentences:  Returning to Canada by 1928, Croil was appointed Station Commander of RCAF Station Borden in Ontario which at that time was one of a very few RCAF training bases.Returning to Great Britain for further advanced training, Croil attended the Imperial Defence College.Crossing back across the Atlantic once more, in 1934 Croil was appointed Senior Air Officer with the RCAF making him the head of the RCAF.