What is the upper limit of Class E airspace?

The upper limit of Class E airspace is generally defined to extend up to 18,000 feet Mean Sea Level (MSL). This level serves as a transition to the overlying Class A airspace, which begins at 18,000 feet MSL. Class E airspace is used to provide air traffic control services for IFR (Instrument Flight Rules) operations and also allows for VFR (Visual Flight Rules) operations under certain conditions.

Class E airspace can exist in various configurations at different altitudes, but it primarily serves to regulate the airspace below 18,000 feet MSL while ensuring the safe separation of air traffic. For instance, it may extend from the surface in some areas or start at higher altitudes in others, so understanding that 18,000 feet is the upper limit for Class E airspace is crucial for pilots and air traffic management.