An Air Force T-50 trainer jet crashed Wednesday during a training session in the southeastern city of Gwangju, killing both pilots.

The plane went down around 1.8 kilometers east of the runway in the Air Force First Fighter Wing, officials said. A major and a captain, both in their 30s, were aboard the domestically produced supersonic jet.

“The trainer jet, all of a sudden, fell down and tumbled over the ground,” a witness told reporters.

Air Force authorities are investigating the exact cause while presuming that an accident might have occurred during the landing process.

It is the second crash of a T-50 jet. A T-50B, designed for acrobatic flight, crashed last November due to a maintenance error.

Korea Aerospace Industries, the country’s sole aircraft maker, developed the T-50 with technological assistance from the U.S. defense giant Lockheed Martin. It has a maximum speed of Mach 1.5 with a maximum range of about 1,500 kilometers.

In May 2011, KAI signed a $400 million contract with Indonesia to sell 16 T-50s. The first batch of T-50s is to depart for Indonesia next month.

By Song Sang-ho (sshluck@heraldcorp.com)