14 C.F.R. § 305.10
Investigations shall be attended only by the witnesses and their counsel, the administrative law judge, the Investigation Attorney, other DOT personnel concerned with the conduct of the proceeding and the official stenographer. All orders initiating investigations, motions to quash or modify investigation subpenas, orders disposing of such motions, documents, and transcripts of testimony shall be part of the record in the investigation. Unless DOT determines otherwise, all orders initiating investigations which do not disclose the identity of the particular persons of firms under investigation shall be published in the FEDERAL REGISTER. Except as otherwise required by law, the remainder of the record of such proceedings shall constitute internal DOT documents which shall not be available to the general public. The use of such records in DOT proceedings subject to part 302 of the Rules of Practice shall be governed by §§ 302.25(g) and 302.12 of this chapter and by the law of evidence applicable to DOT proceedings.
14 C.F.R. §305.10