A total non-event, and the pilots were probably not even aware of each other. If they were contrailing, they would have been up in the 30k'+ region, separated by at least 2k'. At that altitude, there would have been no interaction between them at all. You purely saw one aeroplane passing well beneath another and turning, but at no stage having anything to do with the other. Rather than hundreds watching, you may have been one of only half a dozen, and only in your immediate vicinity would it have appeared as if they even came horizontally close to each other.