Authorities have launched an investigation after a potential mid-air collision between a Turkish Airlines (THY) and a SunExpress aircraft was narrowly averted over North Macedonia, a report said on Tuesday.

The THY Airbus A321-200 was flying from Madrid to Istanbul, while the SunExpress Boeing 737-800 was en route to London Gatwick from Dalaman.

The incident occurred on Sept. 7, prompting an investigation by the North Macedonian Civil Aviation Authority, which classified the event as "serious."

The official probe will look into the incident to determine the cause and assess safety protocols, the Ihlas News Agency (IHA) reported.

The two aircraft came dangerously close while flying at 36,000 feet over the skies near Skopje. That triggered the Traffic Collision Avoidance System (TCAS), which issued warnings to both planes.

The system instructed the SunExpress aircraft to climb, while the THY plane received instructions to descend to 34,000 feet.

Both sets of pilots executed the necessary avoidance maneuvers before safely resuming their respective flights.

SunExpress is a joint venture between Turkish Airlines and Lufthansa.