Air traffic controllers received no response to several altitude warnings issued to a pilot in a fatal crash of two small planes over a Montreal-area shopping mall, audio recordings show.

The crash happened on Friday afternoon in Saint-Bruno-de-Montarville, Que. One of the planes, flown by a 23-year-old man, landed on the roof of Promenade Saint-Bruno and the other, flown by a 21-year-old man, crashed in the parking lot. The 21-year-old pilot died, while the 23-year-old pilot sustained serious injuries.

The planes were both Cessna 152 aircrafts operated by Cargair, the biggest flying school in Quebec.

The Transportation Safety Board is continuing its investigation but in audio recordings of communications between the 23-year-old and air traffic control, the pilot is warned four times to adjust his altitude as he approached the runway. The pilot did not respond.

According to sources, the two pilots involved in the crash were pilots in training from China and there have been concerns there may have been issues with a language barrier.

But Jean-Marc Ledoux, regional manager for air investigations with the Transportation Safety Board, said federal regulations require licensed pilots to pass a language proficiency test in English or French. Those who are only proficient in French are not allowed to enter into certain airspaces where air traffic controllers only speak in English.

“This will be looked at by the investigators, what was the test that was conducted,” he said. “Did the individual pass the test? The language part of this will be looked at, for sure.”

Ledoux is urging patience during the investigation and said the public should not jump to any conclusions.

He said several factors could have contributed to that silence.

“We have to consider a lot of things before coming to any conclusion. Understanding why a person takes several times to reply or correctly reply to an instruction from an air traffic controller might depend on several things. Does he have problems with the radio? Was he very busy on the flight deck with something else?”

Ledoux added that a malfunctioning microphone or sun glare may also have played a role.

The wreckage of both craft has been sent to a TSB facility in Ottawa for further analysis.

Meanwhile, Daniel Adams, operations manager at Cargair, the school training the two pilots, says it’s the first time anything like his has happened in the company’s history and there may have been a communication issue. He said both pilots were used to flying in the area and knew procedures well.

The shopping mall is about five kilometres away from the Montreal Saint-Hubert Longueuil Airport where the flight school is based.