What altitude must be maintained for obstacle clearance during IFR flights?

The correct answer is the Minimum Enroute Altitude (MEA). This altitude is specifically designed to ensure safe navigation and obstacle clearance in IFR operations. MEA provides a guarantee that aircraft can safely navigate between waypoints, with sufficient vertical separation from terrain and obstacles.

In addition to being safe, the MEA also ensures that aircraft can maintain reliable communication and navigation. When flying at or above this altitude, pilots can be confident that they will not encounter any obstacles that exceed the specific clearance requirements set by the FAA.

Other options may pertain to altitude requirements in different contexts but do not specifically address the necessity for obstacle clearance during an IFR flight. For instance, while Minimum Safe Altitude is relevant for ensuring safety in specific geographic areas, it is not universally applicable during flight segments as the MEA is. Mean Sea Level serves as a reference for various altitudes but doesn't pertain directly to obstacle clearance. Maximum Allowed Altitude indicates the upper limit of altitude a pilot can fly under certain airspace classifications but does not directly contribute to safe obstacle clearance. Understanding MEA is crucial for IFR pilots to ensure safe operations while navigating through controlled airspace.