(a) The amounts of financial protection required under this part may be furnished and maintained in the form of:
(1) An effective policy of liability insurance from private sources; or
(2) Adequate resources to provide the financial protection required by Sec. Sec. 140.11, 140.12; 140.13 or Sec. 140.13a; or
(3) Such other type of financial protection as the Commission may approve; or
(4) Any combination of the foregoing.
(b) In any case where the Commission has approved proof of financial protection filed by a licensee the licensee shall not substitute one type of financial protection for another type without first obtaining the written approval of the Commission. [25 FR 2944, Apr. 7, 1960, as amended at 42 FR 49, Jan. 3, 1977]