An aircraft may not be operated in common carrier intrastate service in this State until a permit for it has been obtained from the Commission. The permits may be issued by the Commission at any time during the year, and for such length of time as the Commission may deem best for the public convenience and necessity. Unless a date of expiration is shown on it, a permit will continue in effect until revoked or cancelled by the Commission. Permits may not be transferable, except by order of the Commission. All permits will be subject to the limitation that the operations authorized by them shall be started within 30 days from the date of the permit.