Two pilots were killed Tuesday when a military plane crashed in Ukraine during an exercise, according to the General Staff.

The Su-27 air force fighter jet crashed during a training as part of ongoing NATO drills in the Vinnytsia region, according to a written statement,

One pilot was a U.S. national, said local media reports.

The exercise. Clear Sky 2018, began Oct. 8 in Ukraine and is expected to run until Oct. 19.

The U.S., U.K., Belgium, Denmark, Estonia, Netherlands, Poland and Romania are also attending NATO’s aerial military exercises in western Ukraine.