(a) In addition to the data for each reportable flight required to be reported by this part, a reporting carrier may report to DOT for every other nonstop domestic flight that it schedules, the reportable flight data specified in this part.

(b) Any air carrier that is not a reporting carrier may file the data specified in this part for every reportable flight that it schedules, or for every nonstop domestic flight that it schedules.

(c) Voluntary reports containing information not required to be filed (1) must be submitted in the same form and manner, and at the same time, as reports containing data required to be filed, and (2) must be accompanied by a written statement describing in detail the information that is being voluntarily submitted. A carrier that files a voluntary report must continue to do so for a period of not less than 12 consecutive months.