Class E refers to a category of airspace in the United States that is controlled by the Federal Aviation Administration (FAA). It typically exists at altitudes between 1,200 feet above ground level and 18,000 feet, where pilots must follow specific regulations for flying. Class E airspace is designed to provide a safe environment for both visual and instrument flight rules. In Class E airspace, pilots are not required to communicate with air traffic control (ATC) unless they are operating under instrument flight rules or in certain situations. This airspace can be found around airports, as well as in areas where air traffic is less dense, allowing for more flexibility in flight operations.