29 CFR §1207.3

1. (a)Neutrals appointed by the National Mediation Board. All neutral persons appointed by the National Mediation Board under the provisions of § 1207.1 (b) and (c) will be compensated by the Mediation Board in accordance with legislative authority. Certificates of appointment will be issued by the Mediation Board in each instance.
2. (b)Neutrals selected by the parties.
   1. (1)In cases where the party members of a PL Board created under Public Law 89-456 mutually agree upon a neutral person to be a member of the Board, the party members will jointly so notify the Mediation Board, which Board will then issue a certificate of appointment to the neutral and arrange to compensate him as under paragraph (a) of this section.
   2. (2)The same procedure will apply in cases where carrier and employee representatives are unable to agree upon the establishment and jurisdiction of a PL Board, and mutually agree upon a procedural neutral person to sit with them as a member and determine such issues.