A method of operating an aircraft electrical power distribution system comprises determining a measure of ambient pressure; and setting a target operating voltage in accordance with the measure of ambient pressure. The method further comprises controlling the operating voltage in accordance with the set target operating voltage. The target operating voltage may refer to a distribution voltage of the aircraft. An aircraft electrical power distribution system is also disclosed, comprising: a sensor configured to determine a measure of ambient pressure; a controller configured to set a target operating voltage in accordance with the measure of ambient pressure, and a voltage regulator configured to regulate the operating voltage in accordance with the set target value.