FAA Federal Aviation Regulations (FARS, 14 CFR)

(a) A person may submit a motion for leave to intervene as a party. Except for good cause shown, a motion for leave to intervene shall be submitted not later than 10 days after the notice of hearing and hearing order.

(b) If the hearing officer finds that intervention will not unduly broaden the issues or delay the proceedings and, if the person has a property or financial interest that may not be addressed adequately by the parties, the hearing officer may grant a motion for leave to intervene. The hearing officer may determine the extent to which an intervenor may participate in the proceedings.

(c) Other persons may petition the hearing officer for leave to participate in the hearing. Participation is limited to the filing of post-hearing briefs and reply to the hearing officer and the Associate Administrator. Such briefs shall be filed and served on all parties in the same manner as the parties' post hearing briefs are filed.

(d) Participation under this section is at the discretion of the FAA, and no decision permitting participation shall be deemed to constitute an expression by the FAA that the participant has such a substantial interest in the proceeding as would entitle it to judicial review of such decision.