Compliance with approved routes and limitations: Domestic and flag operations

This regulation requires pilots flying scheduled air carrier operations under Part 121 to stick strictly to the routes and operational limitations listed in their airline's operations specifications (OpSpecs). You cannot fly a scheduled flight over any route or route segment that isn't specifically approved in the OpSpecs, and you must follow all limitations spelled out in those specifications.

In practice, this means your airline's dispatch and flight planning departments will only assign you routes that have been approved by the FAA and documented in the OpSpecs. These specifications detail approved airways, airports, alternate airports, and various operational constraints specific to your carrier's certificate. If a route isn't in the OpSpecs, you can't legally fly it in scheduled service, even if it seems operationally sound. This ensures the FAA maintains oversight of where and how each airline operates, and that routes have been properly evaluated for that carrier's specific capabilities and limitations.

*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.*