Obsolete certificates and ratings
Read the official ruleThis regulation identifies old pilot certificates that are no longer valid for exercising pilot privileges.
Free-balloon certificates issued before November 1, 1973, cannot be used anymore. If you hold one of these ancient certificates, you'd need to obtain a current pilot certificate to fly.
Category ratings without class ratings are also obsolete. The regulation specifically lists rotorcraft, lighter-than-air, helicopter, and autogyro. Modern pilot certificates require both a category AND a class rating to be valid. For example, you can't just have "rotorcraft" on your certificate—you need "rotorcraft" with a specific class like "helicopter" or "gyroplane."
In practice, this regulation rarely affects pilots since these obsolete certificate formats haven't been issued in decades. If you somehow possess one of these old certificates, you'll need to meet current certification standards before exercising pilot privileges.
*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.*