Final answer:
The typical maximum airspeed allowed underlying Class B Airspace in the U.S. is 200 knots, equivalent to approximately 230 miles per hour or 370 kilometers per hour.
Step-by-step explanation:
The maximum airspeed allowed underlying Class B Airspace is specific to aviation regulations rather than being a physical property determined by aerodynamics or physics involved in wing design.
However, in the United States, it's typically 200 knots (which is about 230 miles per hour or 370 kilometers per hour) for aircraft flying at or below 2,500 feet above the surface within 4 nautical miles of the primary airport's Class B airspace.