Which altitude is not permissible for VFR flight above the maximum?

VFR (Visual Flight Rules) operations have specific altitude limits that must be adhered to ensure safety and compliance with aviation regulations. The key aspect of this regulation stipulates that pilots must operate below specific altitudes to maintain visual reference and to avoid issues such as oxygen deprivation at higher altitudes.

In this context, 13,000 feet represents a critical altitude limit for VFR operations. Above this altitude, pilots are required to have supplemental oxygen if flying for extended periods. Operating at or above this altitude without the necessary precautions would not comply with safety regulations, making it an improper choice for a VFR flight.

The other altitude options present varying compliance levels with VFR regulations; those who fly at or above 11,500 feet and 12,500 feet are still within acceptable limits as long as they follow the corresponding regulations, such as oxygen requirements. Specifically, the major inflection point occurs at 13,000 feet where the requirements change significantly compared to lower altitudes, thus making it the altitude not permissible for VFR purposes unless appropriately equipped and prepared.