I had an odd change to my Thanksgiving itinerary. An AUS-MSP-BOS got switched to an AUS-CVG-BOS, leaving and arriving at roughly the same times. The schedule on my original AUS-MSP-BOS hadn't changed, and the agent, who could see when the change was made, could see no reason for it. My wife was on a separate PNR with the same itinerary but hers never got changed. The agent easily set things back to where they were but I was weirded out by the whole thing. I only noticed it by chance. Imagine our surprise if we had arrived at the airport and found we were on different flights.