MSN had a great article from the stranger side of travel called 10 wacky complaints about air travel. You might be surprised what people complain about. My favorite complaint was this one:

Early bird. Complaints about late arrivals are so common that I recite the canned response by rote: “I am sorry for your inconvenience. Please check with the gate agent or customer service representative for connection information But only twice have I had a passenger complain that the flight was arriving too early. What to say? Perhaps, I am sure we will do better to delay you next time”?