A Russian fighter jet had a "near miss" with a US military plane "somewhere around midnight" on Oct. 17, which US sources say was caused by the Russian pilot failing to see the American aircraft in the dark.
Lieutenant General Jeff Harrigian, commander of the US Air Force Central Command told NBC News that the aircraft were "inside of half a mile" of each other -- close enough to feel each other's jet wash.
According to Harrigian, situations like this have increased over the last six weeks, especially in Syria's northwest. He says that a Russian aircraft intercepts a US one "every ten days-ish."
In some cases, incidents like this are "not a big deal." But this one was a little different. "I think it's important to recognize this one got our attention."
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"We called the Russians about it and made sure they knew we were concerned."
RT reports that it was, in fact, the Russians who first picked up the phone to ask for an explanation.
The Russian Defense Ministry says that the American plane failed to follow its flight plan by dropping over half a mile from it's declared altitude, in violation of the flight security rules near the eastern Syrian city of Deir ez-Zor.
The Russian Defense Ministry added that, despite the dangerous incident, it believed that sufficient cooperation between the Russian and American militaries had been established.
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US and Russian officials met in May to discuss flight safety over Syria, according to the Department of Defense.
The Wall Street Journal reports that the incident led to a renewal of those flight safety discussions. In a statement, Russia announced that both militaries would "sign documents on safety in the sky of Syria soon," and, "All technical issues are agreed upon."
President Obama said that even though the US was making progress on avoiding confrontation with the Russians, strategic coordination was not discussed. "Where we will continue to differ," he said, "is in the basic set of principles and strategies we are pursuing inside of Syria."
The US will continue to target ISIS in Syria, and Russia will continue to target opponents of Syrian President Bashar al-Assad, including groups that, according to US officials, are backed by the CIA.