At what altitude are MEAs shown in MSL altitudes?

The Minimum Enroute Altitude (MEA) is depicted in Mean Sea Level (MSL) altitudes for specific altitude ranges set by air traffic management practices. MEAs indicate the lowest altitude that ensures adequate obstacle clearance and reliable navigational signal reception along an air route.

For altitude considerations, MEAs are typically shown in MSL for altitudes above 18,000 feet MSL primarily because this is the transition altitude where aircraft move from lower altitude airspace to the National Airspace System’s upper altitude environment. In the United States, aircraft operate under a different set of regulations above this altitude, and it becomes increasingly important for pilots to rely on MSL to maintain situational awareness and safety in navigation.

The specific thresholds, such as below 18,000 feet, often utilize different parameters, and MEAs may also be displayed differently in those ranges. Therefore, the choice that accurately reflects the threshold where MEAs begin to be shown in MSL is the altitude above 18,000 feet.