A system for determining a performance status of an environmental control system, ECS, for a vehicle, the system comprising: a memory, the memory being configured to store aircraft data (164, 202), weather data (166, 206, 208), and trending data (156, 165), the trending data (156, 165) comprising past compressor exit temperatures and past pack temperatures; and processing circuitry communicatively coupled to the memory, the processing circuitry being configured to: determine, based on one or more of the aircraft data (164, 202), the weather data (166, 206, 208), or the trending data (156, 165), an estimated compressor exit temperature (218, 300); receive, from a first temperature sensor (16a, 16b, 20a, 20b, 60), a measure of a current compressor exit temperature (302, 304); determine, based on the estimated compressor exit temperature (218, 300) and the current compressor exit temperature (302, 304), a current residual compressor exit temperature; determine, based at least in part on the current residual compressor exit temperature, whether a first residual condition is met; determine, based on the determination of whether the first residual condition is met, a first performance status of the ECS; receive, from a second temperature sensor (16a, 16b, 20a, 20b, 60), a measure of a current pack temperature; determine, based at least in part on the current pack temperature, whether a first pack condition is met; determine, based on the determination of whether the first pack condition is met, a second performance status of the ECS; and provide, based on at least one of the first performance status or the second performance status, an indication of the performance status of the ECS. a memory, the memory being configured to store aircraft data (164, 202), weather data (166, 206, 208), and trending data (156, 165), the trending data (156, 165) comprising past compressor exit temperatures and past pack temperatures; and processing circuitry communicatively coupled to the memory, the processing circuitry being configured to: determine, based on one or more of the aircraft data (164, 202), the weather data (166, 206, 208), or the trending data (156, 165), an estimated compressor exit temperature (218, 300); receive, from a first temperature sensor (16a, 16b, 20a, 20b, 60), a measure of a current compressor exit temperature (302, 304); determine, based on the estimated compressor exit temperature (218, 300) and the current compressor exit temperature (302, 304), a current residual compressor exit temperature; determine, based at least in part on the current residual compressor exit temperature, whether a first residual condition is met; determine, based on the determination of whether the first residual condition is met, a first performance status of the ECS; receive, from a second temperature sensor (16a, 16b, 20a, 20b, 60), a measure of a current pack temperature; determine, based at least in part on the current pack temperature, whether a first pack condition is met; determine, based on the determination of whether the first pack condition is met, a second performance status of the ECS; and provide, based on at least one of the first performance status or the second performance status, an indication of the performance status of the ECS. determine, based on one or more of the aircraft data (164, 202), the weather data (166, 206, 208), or the trending data (156, 165), an estimated compressor exit temperature (218, 300); receive, from a first temperature sensor (16a, 16b, 20a, 20b, 60), a measure of a current compressor exit temperature (302, 304); determine, based on the estimated compressor exit temperature (218, 300) and the current compressor exit temperature (302, 304), a current residual compressor exit temperature; determine, based at least in part on the current residual compressor exit temperature, whether a first residual condition is met; determine, based on the determination of whether the first residual condition is met, a first performance status of the ECS; receive, from a second temperature sensor (16a, 16b, 20a, 20b, 60), a measure of a current pack temperature; determine, based at least in part on the current pack temperature, whether a first pack condition is met; determine, based on the determination of whether the first pack condition is met, a second performance status of the ECS; and provide, based on at least one of the first performance status or the second performance status, an indication of the performance status of the ECS.