The FAA guidelines are that no two planes can be within 5 miles of one another at the same altitude, and must be at least 1000 feet apart vertically when crossing at different altitudes. I've been flying roundtrip from Kansas City to Philadelphia twice a month since July, and I can't even count how many planes I've seen. When I flew home the Wed before Thanksgiving, I was up to ~30 on that flight alone when I stopped counting halfway. The majority of the planes I see are usually well out in the distance at varying altitudes. However, there have been several that crossed paths below us that I could make out which airline it was...Northwest and Southwest to be specific.
