Which of the following actions will NOT improve aircraft performance when altitude is increased?

Increasing drag does not contribute to improved aircraft performance at higher altitudes. When flying at higher altitudes, aircraft performance generally deteriorates due to thinner air, which leads to a reduction in engine power and lift. Reducing weight is a beneficial action because it enhances the aircraft's power-to-weight ratio, allowing it to climb more effectively and maintain performance. Adjusting trim can also optimize the aircraft’s aerodynamic efficiency, making it easier to fly and reducing unwanted control pressures, which is particularly important at higher altitudes where performance is already challenged.

However, increasing drag directly counters any efforts to improve performance. Drag requires additional thrust to maintain speed and altitude, which becomes more critical as the air becomes thinner. Therefore, while reducing weight and adjusting trim are both effective strategies for maintaining or enhancing performance at increased altitudes, increasing drag has the opposite effect and is not a method to improve aircraft performance.