; or (2) close such investigation. (b) Extension (1) In general If, upon review of the facts and status of an investigation described in subsection (a), the Administrator determines that the time provided to make a final determination or close such investigation is insufficient, the Administrator shall approve an extension of such investigation for 2 years. (2) Additional extensions The Administrator may approve consecutive extensions under paragraph (1). (c) Delegation The Administrator may not delegate the authority to approve an extension described in subsection (b) to anyone other than the leadership of the Administration as described in section 106(b) of title 49, United States Code. 806. All makes and models authorization (a) In general (1) Unlimited letter of authorization Not later than 1 year after the date of enactment of this Act, the Administrator shall take such action as may be necessary to allow for the issuance of letters of authorizations to airmen with the authorization for— (A) all types and makes of experimental high–performance single engine piston powered aircraft; and (B) all types and makes of experimental high–performance multiengine piston powered aircraft. (2) Requirements An individual who holds a letter of authorization and applies for an authorization described in paragraph (1)(A) or (1)(B)— (A) shall be given an all-makes and models authorization of— (i) experimental single–engine piston powered authorized aircraft; or (ii) experimental multiengine piston powered authorized aircraft; (B) shall hold the appropriate category and class rating for the authorized aircraft; (C) shall hold 3 experimental aircraft authorizations in aircraft of the same category and class rating for the authorization sought