14 CFR § 91.859
Modification to meet Stage 3, Stage 4, or Stage 5 noise levels
July 13, 2020
For an airplane subject to §91.801(c) of this subpart and otherwise prohibited from operation to or from an airport in the contiguous United States by §91.855, any person may apply for a special flight authorization for that airplane to operate in the contiguous United States for the purpose of obtaining modifications to meet Stage 3, Stage 4, or Stage 5 noise levels.
[Docket FAA-2015-3782, Amdt. 91-349, 82 FR 46132, Oct. 4, 2017]