An outer panel-mediated cooling system for an aircraft, comprising: an outer shell including an outer panel and an inner panel located inward of the outer panel; a heat source chamber that is located inward of the inner panel and in which a gas receives heat from a heat source; a cooling path that is located between the outer and inner panels, into which (i) a pressurized gas or (ii) the pressurized gas and a return gas from the heat source chamber flows, in which the at least one gas releases heat outside through the outer panel to change into a cooled gas, and out of which the cooled gas flows; a non-cooling path that is located between the outer and inner panels (21, 22) and thermally insulated from the cooling path and the outer panel and through which at least one of the pressurized gas and the return gas from the heat source chamber passes; a mixing chamber into which the cooled gas leaving the cooling path and an uncooled gas leaving the non-cooling path flow, in which the cooled gas and the uncooled gas are mixed to form a mixed gas, and out of which the mixed gas flows toward the heat source chamber; a flow rate regulating valve that includes at least one of a first flow rate regulating valve configured to regulate a flow rate of the cooled gas flowing from the cooling path toward the mixing chamber and a second flow rate regulating valve configured to regulate a flow rate of the uncooled gas flowing from the non-cooling path toward the mixing chamber; a pressurized gas line that is connected to an inlet of the cooling path and that delivers the pressurized gas to the cooling path, the pressurized gas being produced by compressing outside air to a pressure higher than that of the gas in the cooling path; a third flow rate regulating valve configured to regulate a flow rate of the pressurized gas flowing through the pressurized gas line toward the cooling path; a first temperature sensor configured to detect a temperature of the gas in the cooling path; a first humidity sensor configured to detect a humidity of the gas flowing into the cooling path; and a first humidity controller configured to adjust an opening degree of the third flow rate regulating valve to control the humidity detected by the first humidity sensor to a given humidity that does not cause dew formation at the temperature detected by the first temperature sensor. an outer shell including an outer panel and an inner panel located inward of the outer panel; a heat source chamber that is located inward of the inner panel and in which a gas receives heat from a heat source; a cooling path that is located between the outer and inner panels, into which (i) a pressurized gas or (ii) the pressurized gas and a return gas from the heat source chamber flows, in which the at least one gas releases heat outside through the outer panel to change into a cooled gas, and out of which the cooled gas flows; a non-cooling path that is located between the outer and inner panels (21, 22) and thermally insulated from the cooling path and the outer panel and through which at least one of the pressurized gas and the return gas from the heat source chamber passes; a mixing chamber into which the cooled gas leaving the cooling path and an uncooled gas leaving the non-cooling path flow, in which the cooled gas and the uncooled gas are mixed to form a mixed gas, and out of which the mixed gas flows toward the heat source chamber; a flow rate regulating valve that includes at least one of a first flow rate regulating valve configured to regulate a flow rate of the cooled gas flowing from the cooling path toward the mixing chamber and a second flow rate regulating valve configured to regulate a flow rate of the uncooled gas flowing from the non-cooling path toward the mixing chamber; a pressurized gas line that is connected to an inlet of the cooling path and that delivers the pressurized gas to the cooling path, the pressurized gas being produced by compressing outside air to a pressure higher than that of the gas in the cooling path; a third flow rate regulating valve configured to regulate a flow rate of the pressurized gas flowing through the pressurized gas line toward the cooling path; a first temperature sensor configured to detect a temperature of the gas in the cooling path; a first humidity sensor configured to detect a humidity of the gas flowing into the cooling path; and a first humidity controller configured to adjust an opening degree of the third flow rate regulating valve to control the humidity detected by the first humidity sensor to a given humidity that does not cause dew formation at the temperature detected by the first temperature sensor.