14 C.F.R. § 302.26 – Depositions.

(a) For good cause shown, the DOT decisionmaker or administrative law judge assigned to a proceeding may order that the testimony of a witness be taken by deposition and that the witness produce documentary evidence in connection with such testimony. Ordinarily an order to take the deposition of a witness will be entered only if:
1. (1) The person whose deposition is to be taken would be unavailable at the hearing,
2. (2) The deposition is deemed necessary to perpetuate the testimony of the witness, or
3. (3) The taking of the deposition is necessary to prevent undue and excessive expense to a party and will not result in an undue burden to other parties or in undue delay.
(b) Any party desiring to take the deposition of a witness shall make application therefor in duplicate to the administrative law judge or, in the event that an administrative law judge has not been assigned to a proceeding or is not available, to the DOT decisionmaker or Chief Administrative Law Judge, setting forth the reasons why such deposition should be taken, the name and residence of the witness, the time and place proposed for the taking of the deposition, and a general description of the matters concerning which the witness will be asked to testify. If good cause be shown, the administrative law judge, the DOT decisionmaker, or the Chief Administrative Law Judge, as the case may be, may, in his or her discretion, issue an order authorizing such deposition and specifying the witness whose deposition is to be taken, the general scope of the testimony to be taken, the time when, the place where, the designated officer (authorized to take oaths) before whom the witness is to testify, and the number of copies of the deposition to be supplied. Such order shall be served upon all parties by the person proposing to take the deposition a reasonable period in advance of the time fixed for taking testimony.
(c) Witnesses whose testimony is taken by deposition shall be sworn or shall affirm before any questions are put to them. Each question shall be recorded and the answers shall be taken down in the words of the witness.
(d) Objections to questions or evidence shall be in short form, stating the grounds of objection relied upon, but no transcript filed by the designated officer shall include argument or debate. Objections to questions or evidence shall be noted by the designated officer upon the deposition, but he or she shall not have power to decide on the competency or materiality or relevance of evidence, and he or she shall record the evidence subject to objection. Objections to questions or evidence not made before the designated officer shall not be deemed waived unless the ground of the objection is one that might have been obviated or removed if presented at that time.
(e) The testimony shall be reduced to writing by the designated officer, or under his or her direction, after which the deposition shall be signed by the witness unless the parties by stipulation waive the signing or the witness is ill or cannot be found or refuses to sign, and certified in usual form by the designated officer. If the deposition is not signed by the witness, the designated officer shall state on the record this fact and the reason therefor. The original deposition and exhibits shall be forwarded to Department of Transportation Dockets and shall be filed in the proceedings.
(f) Depositions may also be taken and submitted on written interrogatories in substantially the same manner as depositions taken by oral examination. Ordinarily such procedure will be authorized only if necessary to achieve the purposes of an oral deposition and to serve the balance of convenience of the parties. The interrogatories shall be filed in quadruplicate with two copies of the application and a copy of each shall be served on each party. Within seven (7) days after service any party may file with the person to whom application was made two copies of his or her objections, if any, to such interrogatories and may file such cross-interrogatories as he or she desires to submit. Cross-interrogatories shall be filed in quadruplicate, and a copy thereof together with a copy of any objections to interrogatories, shall be served on each party, who shall have five (5) days thereafter to file and serve his or her objections, if any, to such cross-interrogatories. Objections to interrogatories or cross-interrogatories, shall be served on the DOT decisionmaker or the administrative law judge considering the application. Objections to interrogatories shall be made before the order for taking the deposition issues and if not so made shall be deemed waived. When a deposition is taken upon written interrogatories, and cross-interrogatories, no party shall be present or represented, and no person other than the witness, a reporter, and the designated officer shall be present at the examination of the witness, which fact shall be certified by the designated officer, who shall ask the interrogatories and cross-interrogatories to the witness in their order and reduce the testimony to writing in the witness's own words. The provisions of paragraph (e) of this section shall be applicable to depositions taken in accordance with this paragraph.
(g) All depositions shall conform to the specifications of § 302.3 except that the filing of three copies thereof shall be sufficient. Any fees of a witness, the reporter, or the officer designated to take the deposition shall be paid by the person at whose instance the deposition is taken.
(h) The fact that a deposition is taken and filed in a proceeding as provided in this section does not constitute a determination that it is admissible in evidence or that it may be used in the proceeding. Only such part or the whole of a deposition as is received in evidence shall constitute a part of the record in such proceeding upon which a decision may be based.