The Ukrainian General Staff then removed the mention of the US serviceman from the statement, while the US Air Force acknowledged that a US service member "was involved in this incident".
According to an English translation of the statement "the airplane Su-27UB of the Air Forces of the Armed Forces of Ukraine has crashed during the training and combat flight".
The Su-27UB jet was taking part in Clear Sky 2018, a joint military exercise with North Atlantic Treaty Organisation members taking place October 8 through 19 in Western Ukraine. It said a rescue team found the jet's two pilots dead.
The circumstances of the crash are being investigated, the statement said.
"The objective of the exercises is to increase the level of interoperability of our combat aircrafts with the air forces of the United States and other member states of the [NATO] Alliance". "We will provide more information as soon as it becomes available".
The exercise involves about 950 personnel from nine nations, including Belgium, Denmark, Estonia, the Netherlands, Poland, Romania, Ukraine, the United Kingdom and the United States.
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.
U.S. Air Force pilots are now in Ukraine participating in a large-scale multi-national aviation exercise known as "Clear Sky" involving close to 1,000 personnel from North Atlantic Treaty Organisation countries. The post showed F-15C Eagle fighter jets arriving in western Ukraine a week ago.