What is the adjusted minimum flight level for an altimeter setting between 28.91 and 28.42?

The adjusted minimum flight level for an altimeter setting between 28.91 and 28.42 inches of mercury is determined using the standard atmospheric pressure reference. When altimeter settings are below 29.92 inches, which is the standard sea-level pressure, the minimum flight level becomes higher to ensure safe vertical separation of aircraft operating at those altitudes.

In this scenario, the altimeter setting is between 28.91 and 28.42. To calculate the adjusted minimum flight level, the pressure deviation from the standard setting is taken into account. Every decrease of 0.01 inches of mercury below the standard setting increases the minimum flight level by 100 feet.

Given the settings provided, the range (28.91 to 28.42) indicates a decrease from standard pressure. The extent of this decrease and the corresponding adjustments leads to the conclusion that the corrected minimum flight level rises to 1500 feet. This ensures aircraft maintain adequate altitude separation in flight, preventing potential conflicts in airspace.

Thus, the correct answer is 1500 feet.