14 C.F.R. § 234.3
For air transportation taking place before January 1, 2018, this part applies to reportable flights as defined in § 234.2 that are held out to the public by certificated air carriers that account for at least 1 percent of domestic scheduled passenger revenues. As stated in § 234.7 , certain provisions also apply to voluntary reporting of on-time performance by carriers. For air transportation taking place on or after January 1, 2018, this part applies to reportable flights as defined in § 234.2 that are held out to the public by certificated air carriers that account for at least 0.5 percent of domestic scheduled passenger revenues. As stated in § 234.7 , certain provisions also apply to voluntary reporting of on-time performance by carriers.
14 C.F.R. §234.3