The commander of the Donald Cook described the flights as a "simulated attack"
Putin will keep pushing the envelope until someone makes him stop. Current prez not the right man for that job
Former Soviet bloc countries, now Nato members, were alarmed by Russia's rapid annexation of Crimea during the Ukraine crisis in March 2014. That operation caused the biggest chill in relations with Russia since the end of the Cold War in 1991.
Russia's occupation of Georgian territory after a brief war in August 2008 also signalled a Russian readiness to intervene militarily in what it calls its "neighbourhood".
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Nato has also complained of aggressive behaviour by Russian warplanes in the Baltic region. Russia, meanwhile, objects to Nato operating close to its borders, seeing the alliance as an aggressor.
"The thing I worry about the most is freedom of movement. Their snap exercises that they do, I personally am surprised each time they do it. And so you can see why that scares me," Gen Hodges said.
Since 2007 Russia has been training its forces to conduct "any sort of operation" on its borders, he said. A future crisis would probably involve "hybrid" warfare, including "a nasty cyber environment", he added.
Nato and Western leaders say there is clear evidence of Russia supplying heavy weapons and regular troops to the rebels who control a large swathe of Ukraine's Donetsk and Luhansk regions. Moscow denies that, but says some Russian "volunteers" are helping the rebels.
What's your suggestion as to how to make Putin stop?
A car bomb explosion has killed a leading Belarusian journalist and Kremlin critic, Pavel Sheremet, in the Ukrainian capital Kiev.
He hosted a morning news show on Radio Vesti and reported for Ukrayinska Pravda, a popular news website.
The bomb went off as Sheremet, 44, was driving a car belonging to his partner, the website's owner Olena Prytula.
Sheremet had lived in Kiev for five years, after quitting Russian TV because of alleged Kremlin pressure.
The Russian authorities accuse Ukrainian media of distorting news from eastern Ukraine, where pro-Russian rebels are defying Kiev's forces.
Ukraine's Interior Ministry spokesman, Artem Shevchenko, called the car bombing "a brazen murder... aimed at destabilising the situation" in Ukraine.