Beijing’s air traffic controllers have been criticized for using Mandarin Chinese when communicating with flight crew, confusing pilots who don’t understand the language.

The official language of aviation is English to avoid any problems, but three pilots from Southeast Asia-based airlines say it’s not happening enough in the Chinese capital. Speaking on the condition on anonymity, the pilots admitted they became confused when different air traffic controllers changed the runways scheduled for landing in Chinese. The pilots stressed that all pilots and air traffic controllers should speak a common language so they can share common situational awareness, especially in cases of emergency.

An official with the Civil Aviation Administration of China named Li Mao said the practice of using English to communicate with foreign airline pilots and Mandarin for Chinese pilots has been a long-standing one. He did not elaborate further.