Unless otherwise authorized, what is the maximum indicated airspeed below 10,000 feet MSL?

The maximum indicated airspeed below 10,000 feet MSL is set at 250 knots. This regulation is in place primarily for safety reasons. At lower altitudes, aircraft are typically in closer proximity to terrain, other flying airplanes, and urban areas, where higher speeds could lead to greater risks associated with maneuverability and reaction times.

By limiting the maximum airspeed to 250 knots, pilots can have improved control over their aircraft, which is especially important during takeoff, landing, and in the event of emergencies. This regulation is part of the broader set of air traffic management rules designed to enhance safety in the busy airspace below 10,000 feet.

By contrast, the other options represent speeds that exceed this regulatory limit, which would not be permitted without specific authorization or in special circumstances clearly defined by air traffic control or other aviation regulations. It is important for pilots to be aware of these restrictions to ensure compliance and promote safety in the National Airspace System.