An aircraft management system, comprising: an onboard aircraft system arranged onboard each of a plurality of aircraft, comprising: a compressor exit temperature sensor configured to determine a compressor exit temperature at a compressor of an environmental control system, ECS, of the corresponding one of the plurality of aircraft; a data acquisition unit coupled to receive the compressor exit temperature from the compressor exit temperature sensor, an altitude of the corresponding one of the plurality of aircraft, and an ambient temperature, and configured to generate a data report containing at least the compressor exit temperature, the altitude, and the ambient temperature; and a communications system coupled to receive and transmit the data report from the data acquisition unit; and a ground system, comprising: a ground data server coupled to receive the data report from the communications systems of each of the plurality of aircraft, the ground data server including a fouling module configured to determine a fouling condition of an environmental conditioning element of the ECS based on at least the compressor exit temperature, the altitude, and the ambient temperature according to a model for each of the plurality of aircraft, the fouling condition including a condition indicator and a health indicator; the ground data server furthermore including a fusion module coupled to receive the fouling conditions including the condition indicator and the health indicator for each of the pluarlity of aircraft, the fusion module configured to fuse the indicators across the plurality of aircraft, thereby calculating a fused fouling condition and a maintenance module coupled to receive the fused fouling condition from the ground data server and configured to provide an interface for displaying the fused fouling condition to a user on a mobile device. an onboard aircraft system arranged onboard each of a plurality of aircraft, comprising: a compressor exit temperature sensor configured to determine a compressor exit temperature at a compressor of an environmental control system, ECS, of the corresponding one of the plurality of aircraft; a data acquisition unit coupled to receive the compressor exit temperature from the compressor exit temperature sensor, an altitude of the corresponding one of the plurality of aircraft, and an ambient temperature, and configured to generate a data report containing at least the compressor exit temperature, the altitude, and the ambient temperature; and a communications system coupled to receive and transmit the data report from the data acquisition unit; and a compressor exit temperature sensor configured to determine a compressor exit temperature at a compressor of an environmental control system, ECS, of the corresponding one of the plurality of aircraft; a data acquisition unit coupled to receive the compressor exit temperature from the compressor exit temperature sensor, an altitude of the corresponding one of the plurality of aircraft, and an ambient temperature, and configured to generate a data report containing at least the compressor exit temperature, the altitude, and the ambient temperature; and a communications system coupled to receive and transmit the data report from the data acquisition unit; and a ground system, comprising: a ground data server coupled to receive the data report from the communications systems of each of the plurality of aircraft, the ground data server including a fouling module configured to determine a fouling condition of an environmental conditioning element of the ECS based on at least the compressor exit temperature, the altitude, and the ambient temperature according to a model for each of the plurality of aircraft, the fouling condition including a condition indicator and a health indicator; the ground data server furthermore including a fusion module coupled to receive the fouling conditions including the condition indicator and the health indicator for each of the pluarlity of aircraft, the fusion module configured to fuse the indicators across the plurality of aircraft, thereby calculating a fused fouling condition and a maintenance module coupled to receive the fused fouling condition from the ground data server and configured to provide an interface for displaying the fused fouling condition to a user on a mobile device. a ground data server coupled to receive the data report from the communications systems of each of the plurality of aircraft, the ground data server including a fouling module configured to determine a fouling condition of an environmental conditioning element of the ECS based on at least the compressor exit temperature, the altitude, and the ambient temperature according to a model for each of the plurality of aircraft, the fouling condition including a condition indicator and a health indicator; the ground data server furthermore including a fusion module coupled to receive the fouling conditions including the condition indicator and the health indicator for each of the pluarlity of aircraft, the fusion module configured to fuse the indicators across the plurality of aircraft, thereby calculating a fused fouling condition and a maintenance module coupled to receive the fused fouling condition from the ground data server and configured to provide an interface for displaying the fused fouling condition to a user on a mobile device.