Back in June (yes, 2005) I was flying ORD-GSO (Greensboro, NC) and leaving from one end of the C concourse. The problem was that there were two UAX Embraers parked side by side....one to GSO and the other, leaving 5 min later, to GreenVILLE, SC.

Unreal - both planes left about 30 min late as no fewer than 10 pax got on the wrong plane. As I boarded, I asked to co-pilot if "this was the flight to GSO." He looked at me, pulled out the flight plan, and said, "um...looks like it."

Didn't give me that sense of confidence I was looking for, but we made it anyway.