What must an SIC maintain to be eligible for duty?

For a Second-in-Command (SIC) to be eligible for duty, it is essential that they maintain a current medical certificate. This certification is a regulatory requirement that ensures the SIC meets the necessary health standards to operate an aircraft safely. The medical certificate ensures that the pilot does not have any medical conditions that could impair their ability to fly, thus prioritizing safety for both the crew and passengers.

While other certifications like a flight instructor certificate or a commercial pilot license may be valuable for a pilot, they are not mandatory for an SIC's eligibility for duty. Additionally, a specific type rating could be required for certain aircraft operations, but it is not a blanket requirement for all SIC positions. Therefore, maintaining a current medical certificate is the crucial factor for an SIC's duty eligibility.