Which chart provides aeronautical information for en route navigation during IFR at or above 18,000 MSL?

The En Route High Altitude Chart is specifically designed to provide critical aeronautical information for flights operating under Instrument Flight Rules (IFR) at altitudes of 18,000 feet Mean Sea Level (MSL) and above. This chart features relevant navigation information such as jet routes, airways, waypoints, VOR (VHF Omnidirectional Range) navigation aids, and other necessary details that help pilots navigate safely at higher altitudes.

In contrast, the En Route Low Altitude Chart caters to aircraft operating below 18,000 feet, which is not applicable for this scenario. Sectional Charts are primarily intended for visual flight rules (VFR) navigation and do not provide the necessary detail for IFR operations at high altitudes. Terminal Area Charts are focused on operations in the vicinity of airports and are not suitable for en route navigation above 18,000 feet. Therefore, the En Route High Altitude Chart is the correct choice for IFR navigation at the specified altitude.