By itself, this certificate does not permit the pilot to set up an operation that carries members of the public for hire; such operations are governed by other regulations. Otherwise, a commercial pilot can be paid for certain types of operation, such as banner towing, agricultural applications, and photography, and can be paid for instructing if she or he holds a flight instructor certificate (In the case of lighter-than-air, only a commercial pilot certificate is required to teach for that category). To fly for hire, the pilot must hold a second class medical certificate, which is valid for 12 calendar months if the pilot is 40 years or older; if the pilot is less than 40 years old the certificate is valid for 24 calendar months.