The Vietnam Air Traffic Management Corporation said Friday that the incident happened on the morning of June 19 involving a flight from Hanoi to Da Lat City in the Central Highlands and another from HCMC to Thanh Hoa Province in the north-central region.
The unidentified air traffic controller instructed the Hanoi flight to lower its altitude at around 6:30 a.m. on June 19 when the plane is about to reach the central region, and the air traffic monitoring screen immediately sounded a collision warning.
The controller then instructed the two flights to change directions, ensuring nothing untoward happened.
The Southern Region Air Traffic Services Company has set up a committee to investigate the incident.
Dinh Viet Thang, head of the Civil Aviation Authority of Vietnam, said the collision alert was raised as the two aircraft were flying at the same altitude around 15 km apart, while the minimum distance allowed is 18 km.
But he said the incident was not serious at the air traffic controller and the pilot were in control and could handle the situation.