In 2005, I was on a flight from DCA-DFW on American. The flight was fairly empty with only about 50% of the seats full. It was the last flight of the night, landing around 10 pm.

As we approached DFW, the pilot announced that we would be landing in DFW in about 20 minutes. The guy behind me rang his flight attendant call button. When the flight attendant came over, he said, "Did they say this flight is landing in Dallas? I'm supposed to be on a flight to Houston!" The flight attendant said, "Yes, this is a flight to Dallas." He repeated, "But, I'm supposed to be on a flight to Houston." The flight attendant said "That's impossible, the gate agent wouldn't have let you board if you were supposed to be on a flight to Houston."

The passenger pulled out his boarding pass -- and sure enough, he had a boarding flight for a flight to Houston and had boarded the flight to Dallas.

He asked the flight attendants if there were any other flights to Houston -- they said no because it was 10 pm. He said he had a big meeting he had to be in Houston for the next day. After we landed, I heard him call a rental car company and was going to drive from Houston to Dallas.

So -- yes, this does happen. And yes, sometimes nobody notices until the passengers are in the wrong city!