EEOC’s reg, at 29 C.F.R. §1626.18 :
(a) An aggrieved person may file a civil action against the respondent named in the charge in either Federal or State court under section 7 of the ADEA.
(b) An aggrieved person whose claims are the subject of a timely pending charge may file a civil action at any time after 60 days have elapsed from the filing of the charge with the Commission (or as provided in §1626.12) without waiting for a Notice of Dismissal or Termination to be issued.
(c) The right of an aggrieved person to file suit expires 90 days after receipt of the Notice of Dismissal or Termination or upon commencement of an action by the Commission to enforce the right of such person.
(d) If the Commission becomes aware that the aggrieved person whose claim is the subject of a pending ADEA charge has filed an ADEA lawsuit against the respondent named in the charge, it shall terminate further processing of the charge or portion of the charge affecting that person unless the District Director; Field Director; Area Director; Local Director; Director of the Office of Field Programs; the General Counsel; the Director of Field Management Programs; or their designees determine at that time or at a later time that it would effectuate the purpose of the ADEA to further process the charge.