As used in this part:

(a) Act means Title III of Pub. L. 93-633, the Independent Safety Board Act of 1974 (49 U.S.C. 1901, et seq.).

(b) Board means the National Transportation Safety Board.

(c) Chairman means the Chairman of the National Transportation Safety Board.

(d) Commandant means the Commandant of the Coast Guard.

(e) Major marine casualty means a casualty involving a vessel, other than a public vessel, that results in—

(1) The loss of six or more lives;

(2) The loss of a mechanically propelled vessel of 100 or more gross tons;

(3) Property damage initially estimated as $500,000 or more; or

(4) Serious threat, as determined by the Commandant and concurred in by the Chairman, to life, property, or the environment by hazardous materials.

(f) Public vessel means a vessel owned by the United States, except a vessel to which the Act of October 25, 1919, c. 82 (41 Stat. 305, 46 U.S.C. 363) applies.

(g) Vessel of the United States means a vessel—

(1) Documented, or required to be documented, under the laws of the United States;

(2) Owned in the United States; or

(3) Owned by a citizen or resident of the United States and not registered under a foreign flag.