(a) Except as provided in Subpart E of this part regarding marine casualties, and unless specified by the National Transportation Safety Board (NTSB), the provisions of this subpart apply to all NTSB investigations conducted under its statutory authority.

(b) Consistent with its statutory authority, the NTSB conducts investigations of transportation accidents that include, but are not limited to: accidents, collisions, crashes, derailments, explosions, incidents, mishaps, ruptures, or other similar accidents. Use of the term “accident” throughout this part includes all such occurrences.

(c) Throughout this part, the term “IIC” means the NTSB investigator-in-charge.