Which airspace type requires permission from Air Traffic Control for entry?

Class B airspace is designed to accommodate high-density air traffic around major airports, ensuring the safety and efficiency of operations in areas where many aircraft are communicating with air traffic control (ATC). This type of airspace requires pilots to receive explicit clearance from ATC before entering, indicating the importance of maintaining separation between aircraft during takeoffs and landings in busy airspace.

The requirement for permission in Class B airspace is due to several factors, including the potential for complex traffic patterns and the need for managing both commercial and general aviation traffic safely. Class B airspace covers an area from the surface to an upper limit, typically around 10,000 feet, surrounding large airports where traffic levels are significant.

In contrast, Class G airspace is uncontrolled, allowing pilots to operate without prior clearance, while Class E airspace often requires no ATC permission below specific altitudes. Furthermore, uncontrolled airspace refers to areas where ATC does not provide traffic advisories or separation services, further emphasizing the need for permission only in certain controlled airspaces like Class B.