ATHENS, Greece — Greece's Air Force has declared three days of national mourning after a pilot was killed during a free-fall exercise in southern Greece.

The Air Force said Squadron Leader Nikolaos Vassiliou, 39, was killed when his T-2E Buckeye training jet crashed in a forest near the southern city of Sparta, 220 kilometers (135 miles) southwest of Athens.

Vassiliou's co-pilot ejected safely and was unharmed, the Air Force said.

The T-2, a plane retired from service by the U.S. Navy in 2008, took off from a base in the Kalamata, southern Greece. In the exercise, pilots practice regaining control of the aircraft after a free fall.