In medicine, a person is a carrier if they test positive for a pathogen or a genetic defect without showing any symptoms. This person can unwittingly spread the illness to others without ever knowing he or she is the source.
If your job involves carrying things or people, you work as a carrier. If you deliver newspapers, you are a newspaper carrier. If the job is to transport household items or people, your business is as a common carrier, such as a moving company or an airline. But if you deliver aircraft, you are not an aircraft carrier — that would be a large, flat-decked, military ship where planes can land or take off at sea.