What is a special flight authorization?
A special flight authorization, issued on official FAA letterhead stationery, allows a foreign-registered civil aircraft that does not have the equivalent of a United States standard airworthiness certificate to be operated within the United States.

A civil aircraft registered in a country that is a member of the International Civil Aviation Organization (ICAO) only needs a special flight authorization issued by the FAA.  A civil aircraft registered in a country that is not a member of the ICAO must have both an authorization from the United States Department of Transportation and a special flight authorization issued by the FAA.

How do I obtain a special flight authorization?
To obtain a special flight authorization, apply in the form of a letter, telegram, or telephone facsimile.  The unique application and issuance procedures are provided in FAA Order 8130.2, "Airworthiness Certification of Aircraft and Related Products", Chapter 7, "Special Flight Authorizations for Non-U.S.-Registered Civil Aircraft".

Special airworthiness certificates regulations & policies