The point is that if it was an optical illusion, the planes weren't that close.

When I stand on the ground and see planes in flight, they often appear to be only an inch or two long, and less than a half inch high! Based on this observation, no person should ever be allowed to get into an airplane, because they would die being crushed into such a small space. When viewed from a proper perspective, however, it turns out airplanes are big enough to safely accomodate people.