That same news story shows this graph (I've added the two colored rectangles):
The story is essentially trying to point out how, even though the value of FANG and Netflix were relatively close for some time (shown in pink), a significant difference had emerged in recent weeks (shown in yellow).
I haven't heard the term "air pocket" used to describe something like this very often; it might be a niche use. A more common term for something like this might be cushion. I think the speaker could have just as easily said:
"There’s a pretty good cushion right there between FANG and Netflix.”
This would be a similarly figurative use – although cushion usually refers to some kind of pillow or soft padding, there is also this definition (found at Wordnik):
figuratively a sufficient quantity of an intangible object (like points or minutes) to allow for some of those points, for example, to be lost without hurting one's chances for successfully completing an objective.
Perhaps the speaker has some experience as a pilot, though, so "air pocket" was a natural metaphor. Or maybe the speaker wanted to use an expression that not only highlighted the growing difference in value, but also the steep drop that the FANG index was undergoing at the time. Since air pockets can push planes downward, it's an apt metaphor.