It's not just nationality, there's more!
I have an ex colleague, Irish passport, diplomats son, happened to have been born in Africa due to his fathers' deployment oversees. My current airline needed drivers badly, and soon on the face of it He too was initially accepted. More than met all the criteria. The Airline was thrilled,......then one look at his place of birth when he sent accross his paperwork, and no way. All correspondence was terminated.