49 CFR 801.55 - Interagency and intra-agency exchanges.
(a) Pursuant to 5 U.S.C. 552(b)(5), any record prepared by an NTSB employee for internal Government use is exempt from public disclosure to the extent that it contains -
(1) Opinions made in the course of developing official action by the NTSB but not actually made a part of that official action, or
(2) Information concerning any pending NTSB proceeding, or similar matter, including any claim or other dispute to be resolved before a court of law, administrative board, hearing officer, or contracting officer.
(b) The purpose of this section is to protect the full and frank exchange of ideas, views, and opinions necessary for the effective functioning of the NTSB. These resources must be fully and readily available to those officials upon whom the responsibility rests to take official NTSB action. Its purpose is also to protect against the premature disclosure of material that is in the developmental stage, if premature disclosure would be detrimental to the authorized and appropriate purposes for which the material is being used, or if, because of its tentative nature, the material is likely to be revised or modified before it is officially presented to the public.
(c) Examples of materials covered by this section include, but are not limited to, staff papers containing advice, opinions, or suggestions preliminary to a decision or action; preliminary notes; advance information on such things as proposed plans to procure, lease, or otherwise hire and dispose of materials, real estate, or facilities; documents exchanged in preparation for anticipated legal proceedings; material intended for public release at a specified future time, if premature disclosure would be detrimental to orderly processes of the NTSB; records of inspections, investigations, and surveys pertaining to internal management of the NTSB; and matters that would not be routinely disclosed in litigation but which are likely to be the subject of litigation.