What is the altitude range for Class E airspace if not designated at lower altitudes?

The altitude range for Class E airspace, when not designated at lower altitudes, begins at 14,500 feet MSL (Mean Sea Level) and extends up to but not including 18,000 feet MSL. This class of airspace is primarily intended for en route flight and provides a controlled environment for aircraft operating in that range, facilitating efficient air traffic management.

Class E airspace is used for various purposes, including providing additional airspace for IFR (Instrument Flight Rules) operations. Below 14,500 feet MSL, Class E airspace can be designated at different altitudes by specific requirements, such as in certain terminal areas where it might start lower. However, if not specifically designated, it defaults to starting at 14,500 feet.

The other altitude ranges provided in the options do not reflect the correct boundaries for Class E airspace when it is not designated at lower levels. Understanding the purpose and regulation of Class E airspace is crucial for effective navigation and compliance with air traffic regulations.