14 C.F.R. § 300.10
In cases to be determined on an evidentiary record, a party desiring that a concerned DOT employee disqualify himself or herself from participating in a DOT decision shall file a motion supported by an affidavit setting forth the grounds for such disqualification in the form and within the periods prescribed in § 302.11 of this chapter. Where review of the administrative law judge's decision can be obtained only upon the filing of a petition for discretionary review, such motions must be filed on or before the date answers are due pursuant to § 302.32 . In cases where exceptions are filed to recommended, initial, or tentative decisions or where the DOT decisionmaker orders review of an initial or recommended decision on his or her own initiative, such motions must be filed on or before the date briefs are due pursuant to § 302.35 or § 302.218 , as applicable. Failure to file a timely motion will be deemed a waiver of disqualification. Applications for leave to file an untimely motion seeking disqualification of a concerned DOT employee must be accompanied by an affidavit setting forth in detail why the facts relied upon as grounds for disqualification were not known and could not have been discovered with reasonable diligence within the prescribed time.
14 C.F.R. §300.10