“Now lets talk about separation from other jumpers. First of all, anyone who counts on vertical separation for safety is out of touch with reality. I see people in freefall at 1,500 feet and lower routinely, so just because someone plans to open at 2,500 doesn't mean you should bet your life on it. Everyone needs to open in their own column of air. Horizontal separation is the only guarantee of security.”

Bryan Burke

Skydive Arizona

This quote is from an article by Bryan Burke. I take it as axiomatic that we cannot count on vertical separation for collision avoidance. Anyone who doesn't believe this should think hard about premature deployments, cutaways, and long snivels. I would like to draw particular attention to Bryan's statement about everyone opening "in their own column of air" (my emphasis), since I will return to this concept.