Yes According to official website of China Southern Airlines, the unit training of China Southern Airlines adopts offline centralized mode, and closed small class teaching is implemented. The purpose is to continuously improve the unit resource management ability, effectively control the safety problems caused by human factors, prevent the risk of unfamiliar skills caused by intermittent operation, and realize safe and efficient operation. Therefore, the crew training of China Southern Airlines is totally closed. Unit refers to a group of machines, such as compressor unit, refrigeration unit and generator unit. Generally speaking, the compressor is driven by the prime mover and a set of systems including auxiliary machines.