I was flying from ATL to TPA on Delta last year and I believe we were at cruising altitude. I was gazing out the window (as usual) from the left hand side of the plane. I was amazed to see another plane whiz by directly below us....it came from the right side of the plane so I didn't see it coming and it shocked me. It had to be no more than 500 feet below us. I'm pretty sure it was a DC-9. Anyway, at that altitude & speed, it was awesome to see how quickly we separated from the other plane at a 90 degree angle. I could not help but wonder if that was a normal occurence for pilots?or was it a close call? There was no evasive action taken so I assume the pilots knew it was safely below us.
Anyone else have a story like that to share?