I was in a "near miss" a few years ago, on a flight from IAH-SLC. Our plane actually made a turn to the left, due to another aircraft crossing our path. After a minute or so, we banked right to continue to SLC.

But after this bank, we CROSSED THE CONTRAIL of the other plane, NOT 1000 feet above or below - but AT THE SAME LEVEL and horizontally only a few miles (or less!) apart! (I could see the exhaust through the windows on both the left and right sides of the aircraft!)

That's too close for me!