49 CFR 1114.22: Deposition.

(a) Purpose. The testimony of any person, including a party, may be taken by deposition upon oral examination.

(b) Request. A party requesting to take a deposition and perpetuate testimony:

(1) Should notify all parties to the proceeding and the person sought to be deposed; and

(2) Should set forth the name and address of the witness, the place where, the time when, the name and office of the officer before whom, and the cause or reason why such deposition will be taken.

(c) Limitation under simplified standards. In a case using the Three-Benchmark methodology, each party is limited to one deposition absent advance authorization from the Board.