What safety measure is highlighted by adjusting minimum flight levels according to altimeter settings?

The correct answer emphasizes the importance of vertical separation of aircraft, which is crucial for maintaining safe distances between flights operating in the same airspace. By adjusting minimum flight levels according to varied altimeter settings, air traffic controllers ensure that aircraft remain separated vertically. This practice helps prevent potential collisions and ensures that aircraft can operate safely at different altitudes, particularly when transitioning between different regions with varying atmospheric pressures.

When pilots set their altimeters based on local atmospheric pressure, it guarantees that the indicated altitude reflects the actual horizontal position of the aircraft in relation to sea level. Failure to correctly adjust altimeter settings can lead to aircraft inadvertently flying at the same altitude, increasing the risk of mid-air collisions. Therefore, this measure is integral to overall air traffic safety management, as it directly addresses the spacing between aircraft operating in shared airspace.

Other options, although relevant to aviation operations, do not specifically pertain to the immediate safety concerns associated with vertical separation. Fuel consumption and aircraft efficiency relate more to economic and performance aspects, while flight duration is primarily concerned with route planning and scheduling rather than the immediate safety protocols impacted by altitude adjustments.