you don't have any, who stamps your drawings? Who assumes the liability for the designs? I don't know how it works in the US, but in Canada an Engineer is required to be registered and governed by their professional association to protect the public interest & safety. (I don't know exactly what you do Nick but if it involves designing and building airplanes I would think that is fairly critical work.)
You cannot "engineer" anything in Canada legally without being registered. You can potentially go to jail for falsifying your title here.