In mountainous regions 2, 3, and 4, what is the minimum altitude for IFR aircraft?

The minimum altitude for IFR (Instrument Flight Rules) aircraft in mountainous regions is crucial for ensuring safe operations and obstacle clearance. The correct choice indicates that, within 5 nautical miles of the mountainous terrain, aircraft must maintain at least 1500 feet above the highest obstacle in the area.

This altitude standard is established to provide an additional safety margin that accounts for the potential for sudden altitude changes due to variations in terrain, such as peaks and ridges. In mountainous regions, where terrain can be significantly higher and more variable compared to flat terrain, the additional height is necessary to avoid controlled flight into terrain (CFIT) incidents.

Maintaining this minimum altitude helps pilots ensure that they have a buffer against unexpected rises in terrain and gives them adequate time to respond to any navigational challenges posed by the mountainous environment. Adhering to these altitude restrictions is not only a regulatory requirement but also a vital practice for enhancing safety during IFR operations in such areas.