An applicant may apply for and be granted any class of airman medical certificate as long as the applicant meets the required medical standards for that class of medical certificate.
An applicant must have the appropriate class of medical certificate for the flying duties the pilot intends to exercise. For example, an applicant who exercises the privileges of an airline transport pilot (ATP) certificate must hold a first-class medical certificate. That same pilot when holding only a third-class medical certificate may only exercise privileges of a private pilot certificate. Finally, an applicant does not need to hold an ATP airman/pilot certificate to be eligible for a first-class medical certificate.
The type of medical certification required for each type of flying is determined by Flight Standards.
An airman medical certificate is valid only with the original signature of the AME who performed the examination or with the digital signature of an authorized FAA physician (e.g., Regional Flight Surgeon, manager of the Aerospace Medical Certification Division, Federal Air Surgeon).