Briefs: The Clerk's Office will inform you of the time requirements applicable in your case in a briefing letter. In the typical civil appeal, appellant's brief is due 40 days after the record is received by the Clerk. Appellee's brief is due 30 days after appellant's brief is served. The reply brief, if any, is due 21 days after service of appellee's brief. FRAP 31(a)(1).
The appellant/petitioner is permitted to file only an appellant's brief and a single reply brief (in response to the brief(s) by appellee(s)). Appellee/respondent's brief responds to the arguments in the appellant's brief. FRAP 31(a)(1).
Appendix: An appendix must be filed on the same day a brief is due and served on the opposing party. FRAP 30(a)(3).
Petition for rehearing in banc: A petition for rehearing must be filed within 14 days after entry of judgment or 45 days in a civil case in which the United States is a party. FRAP 40(a)(1).
Extension of Time: If you need an extension of time in which to file your brief and/or appendix, you must request the extension (well before the brief is due) by filing a motion for extension of time with the Clerk. Extensions are disfavored. Failure to file a brief when due or to request an extension may result in dismissal of the appeal for failure to timely prosecute the appeal. 3rd Cir. LAR Misc. 107.2.