Which of the following is a requirement for a student pilot to solo?

For a student pilot to solo, a critical requirement is obtaining a solo endorsement from their instructor. This endorsement signifies that the instructor has assessed the student's flying skills and deemed them proficient enough to operate the aircraft without direct supervision. It validates that the student has completed the necessary ground and flight training, understands the aircraft's systems, and is aware of the procedures necessary for safe operation.

A solo endorsement is an official document that includes the specific make and model of the aircraft that the student is authorized to fly solo. Without this endorsement, the student pilot may not legally operate the aircraft solo, regardless of their flight hours or training.

The other options do not meet the requirements for solo flight. A full private pilot license is necessary for independent flight but is obviously not applicable for a student pilot's solo, while a minimum of 30 flight hours does not guarantee proficiency or authorization without the instructor's endorsement. Additionally, having a second pilot onboard is not a requirement for a student pilot solo, as the essence of solo flight is to operate the aircraft alone.