Ukraine on October 8 began a series of large-scale air force exercises called Clear Sky 2018 with the United States and other North Atlantic Treaty Organisation countries.
The Su-27UB fighter aircraft came down near the village of Ulaniv in Khmelnytsky district, Vinnytsia region, Ukraine, at around 5 p.m.
"The second crewman [of the crashed fighter jet] was a serviceman of the US Air National Guard", the Ukrainian Air Force press center said in a statement.
We will continue to update this story as more information becomes available.
The pilot was assigned to the 144th Fighter Wing based at Fresno, California, said Capt. Christopher Bowyer-Meeder, a spokesman for U.S. Air Forces in Europe.
USAFE-AFAFRICA officials said the both USA and Ukrainian governments are investigating the cause of Tuesday's crash.
The training flight was part of Clear Sky 2018, the largest aviation exercise staged in Ukraine since the former Soviet-bloc country gained independence in the early 1990s.
The pilots were taking part in a "training and combat flight" as part of multinational military exercises with the United States and seven other North Atlantic Treaty Organisation countries.
Officials told Military.com last week that Clear Sky is the first time F-15s from the California Air National Guard have touched down in Ukraine, and the first time the aircraft has been in Ukraine overall since 1998.
An F-15D participating in the exercise "had a minor mechanical issue in flight on Friday that caused the sortie to be cut short", Air Force Maj.