Prohibition on operations during medical deficiency

This regulation prohibits you from acting as pilot in command or required crewmember if you have a medical condition that makes you unable to meet medical certificate requirements or operate safely—even if your medical certificate hasn't expired yet.

If you hold a medical certificate: You cannot fly if you know (or have reason to know) of any medical condition or are taking medication/treatment that would prevent you from meeting the requirements for your medical certificate.

If you fly under BasicMed or sport pilot rules (no medical certificate required): You cannot fly if you know of any condition that would make you unable to operate the aircraft safely.

If you hold both a medical certificate and driver's license for BasicMed: The medical certificate standard applies unless you're operating under BasicMed rules, in which case the "safe operation" standard applies.

This means your personal fitness to fly matters every single flight, regardless of when your medical certificate expires.

*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.*