It peaked at about 10 times in 2014.
The reason it's difficult is that some of that is classified. This is what is publicly available.
On April 19th, 2016. See this statement in context.
April 19th, 2016 / 9:55 a.m.
Deputy Commander, North American Aerospace Defense Command (NORAD), Department of National Defence
It peaked at about 10 times in 2014.
The reason it's difficult is that some of that is classified. This is what is publicly available.
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