Circuit Rule 35Petition for Panel Rehearing and Petition for Hearing or Rehearing En Banc
(a) Time Within Which to File. In all cases in which a party is one of those listed in FRAP 40(a)(1)(A) - (D) [government], the time within which any party may seek panel rehearing or rehearing en banc is 45 days after entry of judgment or other form of decision. In all other cases, any petition for panel rehearing or petition for rehearing en banc must be filed within 30 days after entry of judgment or other form of decision. The time for filing a petition for panel rehearing or rehearing en banc will not be extended except for good cause shown.
The 21 day "deadline" appears to control this case because that is when the order from the Circuit Court becomes effective. If the order is put into effect, the Flynn case becomes closed.
Circuit Rule 41Issuance of Mandate; Stay of Mandate; Remand
(3) Writs. No mandate will issue in connection with an order granting or denying a writ of mandamus or other special writ, but the order or judgment granting or denying the relief sought will become effective automatically 21 days after issuance in the absence of an order or other special direction of this court to the contrary.
Rule 40 has a 14 day deadline to petition for a panel rehearing
DC Circuit Rule 35:(c) Time for Petition for Hearing or Rehearing En Banc. .... A petition for rehearing en banc must be filed within the time prescribed by Rule 40 for filing a petition for rehearing.
DC Circuit Rule 40:Rule 40. Petition for Rehearing by the Division.
(a)(1) Time. Unless the time is shortened or extended by order, a petition for rehearing by the division may be filed within 14 days after entry of judgment.