The plane crashed at around 2:00 p.m. GMT in the Vinnytsia region in west-central Ukraine while performing a flight as part of the Clear Sky 2018 drills, the Ukrainian military prosecutor's office said in a statement.
According to the Ukrainian Military Portal, the accident took place during the multinational military exercise titled "Clear Sky-2018".
"We have seen reports claiming a U.S. casualty and can confirm a U.S. service member was involved in this incident", U.S. Air Forces Europe said in a Tuesday statement.
The Ukrainian General Staff had issued an earlier online statement indicating that both a Ukrainian pilot and an American pilot were on board and killed in the crash.
"We have seen reports claiming a USA casualty and can confirm a USA service member was involved in this incident", it said in a statement, adding that the circumstances of the crash were under investigation. "It is now under investigation and we will continue to provide more information as it becomes available", it added. The goals of the exercise were to enhance regional security and cooperation between Ukraine and North Atlantic Treaty Organisation allies, and other partners in the region.
Exercise Clear Sky 2018 is a multinational exercise that involves approximately 950 personnel from Belgium, Denmark, Estonia, the Netherlands, Poland, Romania, Ukraine, the United Kingdom, and the United States. "Aircraft from California units will include F-15C Eagles and a C-130J Super Hercules", said the Air Force.