28. Unless otherwise specifically authorized, no person may operate an aircraft that has an experimental certificate

Title 14 § 91.319 Aircraft having experimental certificates: Operating limitations.

(c) Unless otherwise authorized by the Administrator in special operating limitations, no person may operate an aircraft that has an experimental certificate over a densely populated area or in a congested airway. The Administrator may issue special operating limitations for particular aircraft to permit takeoffs and landings to be conducted over a densely populated area or in a congested airway, in accordance with terms and conditions specified in the authorization in the interest of safety in air commerce.