I have a question - how close are planes allowed to fly when their paths are about to cross? I am sure there are proximity warnings and what not but I also know those accidents happen, even if not that often.
I was on board of a KLM flight from Amsterdam to Madrid and sometimes in the later part of the flight, if I recall correctly, another plane, flew just below us. Of course, I imagine human vision, mine included, is probably not the most reliable source. However, I saw the plane and in less than 1 second it speeded right below us, so I imagine that it was quite close. However, I felt no turbolence after it passed.
Given that description, can you let me know your thoughts - how close in reality it was? Of course if it helps, I can give you the flight number and day.