Local residents reported seeing the jet lose altitude as it diverted from a civilian neighborhood, according to the Kiev-based Ukrainian Independent Information Agency of News, which quoted a Ukrainian air force statement.
According to the Ukrainian Military Portal, the accident took place during the multinational military exercise titled "Clear Sky-2018".
Petrenko was the experienced Air Force officer, fully trained to act as an instructor during combat missions in both day- and nighttime, in complicated weather conditions.
The U.S. Air Forces in Europe and Africa issued a statement saying it was aware of "reports claiming a U.S. casualty".
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The airplane returned to Joint Base Andrews, an air force facility used by the White House outside Washington , DC. Stephanie Grisham, Trump's communications director, told CNN the incident was a " minor mechanical issue ".
We will continue to update this story as more information becomes available.
The training exercise included US aircraft from the California Air National Guard, including F-15C Eagles and a C-130J Super Hercules, in addition to an F-15D from the 48th Fighter Wing, KC-135s from the Illinois Air National Guard and the 100th Air Refueling Wing. More details will be added as they emerge.
Ukrainian officials first reported the incident, noting that two pilots aboard the Su-27 had been killed in the crash during the joint multi-national exercise with US and other North Atlantic Treaty Organisation air forces in the Khmelnytskyi region, according to The Associated Press.
California units were heavily represented in Clear Sky with F-15C Eagles and C-130J Super Hercules.
The U.S., U.K., Belgium, Denmark, Estonia, Netherlands, Poland and Romania are also attending NATO's aerial military exercises in western Ukraine.