Route width

This regulation establishes how wide a route corridor is for Part 121 airline operations. When flying on established Federal airways, foreign airways, or advisory routes, the route width is simply whatever width those airways already have designated.

For routes that aren't on established airways, the FAA determines an appropriate width based on five factors: terrain clearance needs, minimum altitudes, available navigation aids, how busy the airspace is, and air traffic control procedures in the area. This ensures the route provides adequate safety margins for navigation and obstacle clearance.

In practice, this matters because pilots must stay within the approved route width during flight. Any custom route widths determined by the FAA for non-airway routes will be published in the airline's operations specifications, so flight crews know the lateral limits they must observe when planning and flying those routes.

*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.*