"A Sukhoi-27 plane crashed at around 5 p.m. local time during a training flight", the General Staff of the Armed Forces of Ukrainesaid.
"This is a sad day for the United States and Ukraine", Maj. More details will be added as they emerge.
Ukrainian Air Force pilot and instructor Ivan Petrenko and the U.S. pilot, whom the authorities have identified only as a U.S. Air National Guard officer, were killed in the crash. Gen. Clay Garrison, California ANG commander and Clear Sky exercise director, said in a statement. Nor did it clarify the fate of the US pilot.
"We regret to report that according to the information of the search and rescue team, the bodies of two pilots have been found", said the statement.
No casualties were reported among the civilian population, UNIAN said, quoting the Ukrainian air force command.
The circumstances of the crash are being investigated, the statement said.
"Clear Sky 2018 is a joint and multinational exercise that will involve approximately 950 personnel from nine nations, including Belgium, Denmark, Estonia, the Netherlands, Poland, Romania, Ukraine, the United Kingdom, and the United States", a September news release from the Air Force stated.
The Military Prosecutors Office of Central Region has already opened a criminal case on the "violation of flying rules", reads a statement published on its website on October 16. Cooperation between North Atlantic Treaty Organisation and Kiev has expanded swiftly since Russia's 2014 annexation of Ukraine's Crimean Peninsula. According to the preliminary information, he was the US citizen. The post showed F-15C Eagle fighter jets arriving in western Ukraine a week ago.