A friend of mine (who is notorious in our circle of friends for being disorganized/chronically late etc.) once showed up at OAK (his usual airport) when he was in fact flying out of SFO. However he had time to correct the error because it was a heavy weather day and things at SFO were so delayed.
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For the "misery loves company" folks, there's also this thread in the TravelBuzz forum:
The dumbest travel-related mistake you ever made?