Which certification allows pilots to act as pilot in command of a single engine aircraft?

The Private Pilot Certificate is the appropriate certification that allows pilots to act as pilot in command of a single-engine aircraft. Holding this certificate signifies that a pilot has acquired the necessary skills, knowledge, and flying experience to safely operate a single-engine aircraft under visual flight rules (VFR).

The Private Pilot Certificate is more focused on general aviation and is designed for pilots who do not intend to make flying their career but want to fly for personal or recreational purposes. It encompasses a variety of flying privileges, including the ability to carry passengers and airframe limitations under specific conditions, such as not flying for compensation or hire.

In contrast, the other certifications listed have different scopes and limitations. The Commercial Pilot Certificate allows for more advanced privileges, including flying for compensation, but is not necessary solely for flying single-engine aircraft privately. The Sport Pilot Certificate is limited to specific types of aircraft and does not permit the same scope as the Private Pilot Certificate under certain conditions. The Flight Instructor Certificate primarily enables pilots to teach others how to fly and is not specifically focused on single-engine aircraft operation. Thus, the Private Pilot Certificate is the most appropriate choice for the question about flying a single-engine aircraft.