Flight time limitations: Other commercial flying: airplanes

If you work for a Part 121 supplemental carrier (typically charter or on-demand operations), you cannot accept other commercial flying jobs if the combination would push you over Part 121's flight time limits. The regulation requires you to count all your commercial flying time together—not just your Part 121 hours—when determining compliance with these limits.

This means if you fly cargo charters for a supplemental carrier and also do commercial banner towing or flight instruction on the side, you must track both activities combined. If your Part 121 flying alone would keep you legal, but adding your outside commercial work exceeds the limits, you've violated the regulation.

The practical impact: Part 121 supplemental pilots must carefully manage any side commercial flying jobs. You're responsible for ensuring the total doesn't exceed limits, even though your employer only controls part of your schedule. This is stricter than simply following your company's scheduling—you must self-monitor across all commercial activities.

*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.*