Ukraine has opened a series of large-scale air-force exercises with the United States and seven other NATO countries, the Ukrainian Defense Ministry says.
The 12-day-long Clear Sky 2018 war games are being held in western Ukraine.
Some 700 troops are taking part, half of them from NATO member countries -- the United States, Britain, Netherlands, Belgium, Denmark, Estonia, Poland, and Romania.
U.S. aircraft including F-15C Eagle fighter planes and C-130J Super Hercules military transport planes and drones will train with about 30 Ukrainian aircraft, the ministry said on October 8.
Ukrainian Air Force spokesman Yuriy Ignat said Polish, Romanian, and Ukrainian aircraft will work together "in the air to protect the airspace for the first time."
The aim is "to enhance regional capabilities to secure air sovereignty and promote peace and security through cooperation," a U.S. Air Force statement said.
Concerns have risen about Russia's increased assertiveness, particularly after Moscow's annexation of Ukraine's Crimea region in 2014.