En route navigation facilities

Airlines operating under Part 121 domestic or flag rules must demonstrate that adequate navigation aids exist along every proposed route, including to regular, refueling, provisional, and alternate airports. These aids must be sufficient to navigate with the accuracy required by air traffic control. The airline's operations specifications list which navigation aids are required for routes outside controlled airspace (except for alternate airport routes).

However, navigation aids aren't required for three situations:

• Day VFR flights that can be safely conducted by visual reference to terrain
• Night VFR flights on routes with reliably lighted landmarks sufficient for safe navigation
• Other operations specifically approved by the FAA Flight Standards office

This regulation ensures airlines can navigate accurately in instrument conditions while allowing flexibility for visual operations where terrain or lighting provides adequate guidance.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*