What must a pilot have to act as pilot in command of a complex or high performance airplane?

To act as pilot in command of a complex or high-performance airplane, a pilot must have logged instruction from an authorized instructor and received an endorsement. This requirement ensures that the pilot has the necessary knowledge and skills specific to the complexities presented by these types of aircraft, such as retractable landing gear, flaps, or advanced avionics systems.

Endorsements are part of the training process that verify a pilot's capability to safely operate more advanced aircraft. An authorized instructor assesses the pilot's proficiency in handling the aircraft's unique systems and operations before providing the endorsement, which is mandatory for legal operation.

The other options are not sufficient on their own. Proof of physical fitness is vital for all pilots, but it doesn't specifically address the operational requirements for complex or high-performance aircraft. Similarly, logged flight time in a simulator may help in training but does not meet the regulatory requirements for actual flight without the appropriate endorsement. Certification as an airline transport pilot indicates a high level of training and experience but is not a requisite for operating complex or high-performance airplanes, which only requires the specific endorsement after appropriate instruction.