Two Chinese planes were involved in a near miss in Russian airspace earlier this month in an incident that has sparked fresh concerns over aviation safety.
Recordings of the pilots' discussions with air traffic control suggest that an Air China passenger plane made an unexpected manoeuvre that put it on a potential collision course with an SF Airlines cargo plane.
The manoeuvre had not been requested by air traffic control and the reason why the plane did this is yet to be explained.
However, the recording shows that the air traffic controller had asked another plane in the area to change altitude and one possible explanation is that the Air China pilot had misheard or misunderstood the instruction sent to the other plane.
In the incident, which happened over Tuva, a remote part of Siberia that borders Mongolia, the two planes came within 300-400 feet (around 90-120 metres) of each other, much closer than the global minimum standard of 1,000 feet, according to live tracker Flightradar24.
Radar shows that the near-collision happened when Air China Flight CA967, an Airbus A350 travelling from Shanghai to Milan, started climbing from a height of 34,100 feet to 36,000 feet between 21.39 and 21.52 GMT on Sunday, July 6 (just before 6am the following day Chinese time).
This put it on a potential collision course with SF Airlines CSS128, a Boeing 767 cargo plane flying from Budapest to Ezhou, a city in the central province of Hubei.
Apparent recordings of the discussions between pilots and air traffic control - all conducted in English - started circulating on Chinese social media over the weekend and suggest the Russian controller was directing four planes at the time.
The two other planes - another Air China flight, CA861 travelling from Beijing to Geneva, and Hainan Airlines HU7937, flying between Beijing and Prague - were flying to the northwest of the pair involved in the incident.
Air traffic control asked the Geneva-bound flight and the Hainan Airlines plane to maintain their current altitudes - flight level 360 (or 36,000 feet) and level 340 respectively.
CA967, the Air China flight involved in the near miss, did not receive any instructions at this point but the pilot started speaking just after the Hainan Airlines pilot repeated the controller's instruction.
It is not clear what the Air China pilot said because the audio was interrupted, possibly due to overlapping transmissions, and only the flight number was clearly audible.
Radar information suggests that after the flight began its near-fatal ascent, the two planes were left on a course that had them flying almost directly towards each other.
The pilot on the SF Airlines cargo plane, flying at around 35,000 feet, apparently spotted the potential collision and requested information from air traffic control, which confirmed there was an Airbus A350 in front of the plane.
The controller then put the request to the Hainan Airlines plane on hold and told the two planes on a collision course to take evasive action by veering off in opposite directions.
The near miss triggered an alarm known as the Traffic Collision Avoidance System on both planes, prompting the Air China pilot to ask air traffic control what had caused this to happen.
The controller then asked: "Are you climbing with instruction or without instruction? Confirm, please."
The pilot replied: "No. Thank you."
It is not known who released the recording and it could not be independently verified. Air China, SF Airlines and the Civil Aviation Administration of China have been asked for comment.
The recording circulating online also includes a conversation between the two pilots after they switched to a different communication channel and spoke to each other in Mandarin.
The sound quality meant that parts of the conversation were inaudible, but at one point the cargo pilot was heard to say: "I saw your plane climbing. Did [air traffic control] instruct you to?
"I saw that there was a plane ahead and it was only 20 nautical miles [37km] away and still climbing. Such a crossing altitude is very inappropriate. I guess you also heard me saying 'request traffic information'."
The Air China pilot appeared to blame the female Russian air traffic controller for the incident, saying "the girl" was "making a fuss" and had left everyone "confused".
He later said "we couldn't explain it clearly to them" and "didn't know how to tell them".
The pilot added: "I assume we'll have to write a report on this kind of incident when we get back."
His SF Airlines counterpart replied: "Definitely, without a doubt. I have to report home [to the company] right away."
Recordings of the pilots' discussions with air traffic control suggest that an Air China passenger plane made an unexpected manoeuvre that put it on a potential collision course with an SF Airlines cargo plane.
The manoeuvre had not been requested by air traffic control and the reason why the plane did this is yet to be explained.
However, the recording shows that the air traffic controller had asked another plane in the area to change altitude and one possible explanation is that the Air China pilot had misheard or misunderstood the instruction sent to the other plane.
In the incident, which happened over Tuva, a remote part of Siberia that borders Mongolia, the two planes came within 300-400 feet (around 90-120 metres) of each other, much closer than the global minimum standard of 1,000 feet, according to live tracker Flightradar24.
Radar shows that the near-collision happened when Air China Flight CA967, an Airbus A350 travelling from Shanghai to Milan, started climbing from a height of 34,100 feet to 36,000 feet between 21.39 and 21.52 GMT on Sunday, July 6 (just before 6am the following day Chinese time).
This put it on a potential collision course with SF Airlines CSS128, a Boeing 767 cargo plane flying from Budapest to Ezhou, a city in the central province of Hubei.
Apparent recordings of the discussions between pilots and air traffic control - all conducted in English - started circulating on Chinese social media over the weekend and suggest the Russian controller was directing four planes at the time.
The two other planes - another Air China flight, CA861 travelling from Beijing to Geneva, and Hainan Airlines HU7937, flying between Beijing and Prague - were flying to the northwest of the pair involved in the incident.
Air traffic control asked the Geneva-bound flight and the Hainan Airlines plane to maintain their current altitudes - flight level 360 (or 36,000 feet) and level 340 respectively.
CA967, the Air China flight involved in the near miss, did not receive any instructions at this point but the pilot started speaking just after the Hainan Airlines pilot repeated the controller's instruction.
It is not clear what the Air China pilot said because the audio was interrupted, possibly due to overlapping transmissions, and only the flight number was clearly audible.
Radar information suggests that after the flight began its near-fatal ascent, the two planes were left on a course that had them flying almost directly towards each other.
The pilot on the SF Airlines cargo plane, flying at around 35,000 feet, apparently spotted the potential collision and requested information from air traffic control, which confirmed there was an Airbus A350 in front of the plane.
The controller then put the request to the Hainan Airlines plane on hold and told the two planes on a collision course to take evasive action by veering off in opposite directions.
The near miss triggered an alarm known as the Traffic Collision Avoidance System on both planes, prompting the Air China pilot to ask air traffic control what had caused this to happen.
The controller then asked: "Are you climbing with instruction or without instruction? Confirm, please."
The pilot replied: "No. Thank you."
It is not known who released the recording and it could not be independently verified. Air China, SF Airlines and the Civil Aviation Administration of China have been asked for comment.
The recording circulating online also includes a conversation between the two pilots after they switched to a different communication channel and spoke to each other in Mandarin.
The sound quality meant that parts of the conversation were inaudible, but at one point the cargo pilot was heard to say: "I saw your plane climbing. Did [air traffic control] instruct you to?
"I saw that there was a plane ahead and it was only 20 nautical miles [37km] away and still climbing. Such a crossing altitude is very inappropriate. I guess you also heard me saying 'request traffic information'."
The Air China pilot appeared to blame the female Russian air traffic controller for the incident, saying "the girl" was "making a fuss" and had left everyone "confused".
He later said "we couldn't explain it clearly to them" and "didn't know how to tell them".
The pilot added: "I assume we'll have to write a report on this kind of incident when we get back."
His SF Airlines counterpart replied: "Definitely, without a doubt. I have to report home [to the company] right away."
