For an airplane subject to Sec. 91.801(c) of this subpart and otherwise prohibited from operation to or from an airport in the contiguous United States by Sec. 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 or Stage 4 noise levels. [Doc. No. FAA-2003-16526, 70 FR 38750, July 5, 2005]