What is a common lower limit of Class E airspace?

Class E airspace is typically designated to provide controlled airspace for various types of operations, including those conducted by instrument flight rules (IFR) pilots and for Air Traffic Control (ATC) services. A common lower limit for Class E airspace is indeed 1,200 feet above ground level (AGL), particularly in areas that are not otherwise controlled.

This vertical limit facilitates the transition of aircraft from uncontrolled airspace, where many general aviation activities occur, into a controlled environment as they climb or descend, especially when operating under IFR. This transition is essential for safety, as it helps segregate different types of traffic and ensures that pilots receive the necessary services from ATC.

While other altitudes, such as 3,500, 5,000, and 10,000 feet AGL, can apply under specific conditions or in designated locations, they do not represent the general lower limit for Class E airspace, making 1,200 feet AGL the correct answer as it reflects the standard practice across the National Airspace System.