There is no difference between the method and severity of the medical examination for entry for naval flying duties and that for flying duties with the R.A.F. Prior to appointment to medical boards all medical officers undergo a special course of instruction in the medical examination for fitness for flying. There is a close liaison between the medical department of the R.A.F. and R.N. regarding the medical standards and methods of examination of candidates. Medical boards receive instructions as necessary. In cases of doubt regarding the medical fitness of a candidate for naval flying duties, the case is referred to a civil or Service specialist.