What altitude does the MEA specifically ensure?

The Minimum Enroute Altitude (MEA) specifically ensures the minimum altitude for navigating within a segment of airspace. This altitude guarantees adequate clearance over terrain and obstacles, as well as a reliable signal from the navigational aids along the route. The MEA ensures that pilots maintain enough altitude not only for safe terrain clearance but also to ensure that any navigation systems being used are operational, thus allowing for effective navigation along the route. This altitude is essential for routes that have specific navigational requirements, ensuring that both safety and flight capability are maintained during enroute segments.

In contrast to the other choices, the MEA is not about establishing a minimum safe altitude for visual flights, a maximum altitude related to controlled airspace, or a standard altitude for commercial airliners, which serve different purposes in aviation operations. The primary focus of the MEA is to support navigation and safety during flight, making it a crucial piece of information for pilots.