What is the maximum indicated airspeed allowed below 10,000 feet MSL unless otherwise instructed?

The maximum indicated airspeed allowed below 10,000 feet MSL is 250 knots, which is set by Federal Aviation Administration (FAA) regulations. This rule is designed to enhance safety, minimize noise complaints in congested areas, and reduce the likelihood of wake turbulence encounters. Operating within this speed limit provides a standard that reduces the complexity of airspace management, especially in busy terminal areas.

It is important to note that this speed restriction applies to all aircraft except when otherwise instructed by air traffic control or in certain operational conditions, such as during takeoff and landing phases where specific procedural speeds may differ.

Other options, like 200 knots and 250 MPH, do not apply as the regulation specifically states an indicated airspeed of 250 knots. The use of knots as a unit of measurement is consistent in aviation for airspeed, making it clear why 250 knots is the correct answer in this context.