Before flying in Class B airspace, what additional requirement must be fulfilled apart from having a Mode C transponder?

To legally operate in Class B airspace, pilots must receive clearance from Air Traffic Control (ATC) before entering. This requirement is established to ensure safety and efficient traffic management in these busy airspace areas, where there is a high volume of aircraft, including commercial airliners. When a pilot contacts ATC, they must request permission to enter the airspace. Once ATC provides a clearance, the pilot can safely proceed.

While there are additional requirements, such as having a Mode C transponder, the essential step that distinguishes Class B airspace is the need for ATC authorization. Other options may involve procedures relevant to airspace, but without ATC clearance, a pilot cannot legally enter Class B airspace.