Section 121.115 - Route width(a) Routes and route segments over Federal airways, foreign airways, or advisory routes have a width equal to the designated width of those airways or advisory routes. Whenever the Administrator finds it necessary to determine the width of other routes, he considers the following:(2) Minimum en route altitudes.(3) Ground and airborne navigation aids.(b) Any route widths of other routes determined by the Administrator are specified in the certificate holder's operations specifications.Doc. No. 6258, 29 FR 19195, Dec. 31, 1964, as amended by Amdt. 121-253, 61 FR 2610, Jan. 26, 1996