At night, I look at the planes in the sky and count them. I can normally spot between 2-5 planes, never more.
As the visible sky is always a constant area and there are security distances and aerial ways, is it possible to use a formula/approximation to determine the maximum number of visible planes in the sky?
Assume horizon to horizon visibility.
EDIT - Note to all those who spent some time for me
I didn't imagine this question would be such broad... this was just a though I had last night in my garden.
So, I have no idea how to be more precise... I learned some things of your comments, I am now reading some articles to learn what all that means (new words, moreover in English), and I will enrich the question some further day.
Thanks to all !