Uncontrolled airspace or what type of airspace is not designated as Class A, B, C, D, or E?

Class G airspace refers to uncontrolled airspace which is not designated as Class A, B, C, D, or E. This type of airspace is essentially the portion of airspace where pilots operate without air traffic control (ATC) services, allowing for more freedom in flight operations. Class G airspace typically exists beneath the floors of controlled airspace and extends to the surface, often found in rural or less-populated areas.

In Class G airspace, pilots are responsible for maintaining their own separation from other aircraft and must adhere to visual flight rules (VFR) if they are flying under them. This airspace is significant for recreational pilots and small aircraft operations that do not require ATC services.

Other options such as Class F airspace are not officially recognized by the FAA in the United States, making them less relevant in this context; restricted airspace and temporary flight restrictions are specific types of airspace that have certain limitations or temporary rules imposed, but they do not designate uncontrolled airspace.