SEOUL-- South Korea's Air Force on Wednesday attributed the deadly crashes of two KT-1 trainer jets earlier this month to a set of human errors, including pilot communication failures.

Wrapping up a weekslong probe, its investigation team said a combination of failures in communication between the pilots and among the pilots and air traffic control personnel led to the April 1 crashes that killed four aboard the jets.

The jets went down in a rice paddy in Sacheon, about 300 kilometers south of Seoul, after colliding in midair during a training session, shortly after taking off from a nearby base.

The crashes occurred as three KT-1 trainers -- two in a flight formation and the other on its own -- were flying toward an operational area.

An instructor aboard one of the jets in formation abruptly changed course to avoid clouds and did not properly notify the other jet in the same formation of the change, the team said.

During the process, ground control tower personnel also failed to properly communicate the course change to the pilots.

Such failures caused a collision between the two jets -- one of the jets in formation and the other on a separate route, according to the team.

There was no evidence of mechanical defects, it added.

The Air Force plans to refer to a disciplinary panel those responsible for the crashes, including the instructor in question and air traffic control personnel.

South Korea has operated the homegrown single-engine, two-seat basic training aircraft since 2000.

It was the first mid-air collision of two KT-1 jets, and the first such accident involving any pair of Air Force planes since two F-5E fighter jets collided in 2008.

Source: Yonhap News Agency