Courtesy of Steve P.
A group of Sergeants and a group of Air Force Officers take a train to a conference. Each Officer holds a ticket, but the entire group of Sergeants has bought only one ticket for a single passenger. The Officers are just shaking their heads and are secretly pleased that the arrogant Sergeants will finally get what they deserve.
Suddenly one of the Sergeants calls out: "The conductor is coming!" At once, all the Sergeants jump up and squeeze into one of the toilets. The conductor checks the tickets of the Officers. When he notices that the toilet is occupied he knocks on the door and says: "Ticket, please!" One of the Sergeants slides the single ticket under the doors and the conductor continues merrily on his round.
For the return trip the Officers decide to use the same trick. They buy only one ticket for the entire group but they are baffled as they realize that the Sergeants didn't buy any tickets at all. After a while one of the Sergeants announces again: "The conductor is coming!" Immediately all the Officers race to a toilet and lock themselves in.
All the Sergeants leisurely walk to the other toilet. Before the last Sergeant enters the toilet, he knocks on the toilet occupied by the Officers and says: "Ticket, please!"
And the moral of the story? Officers like to use the methods of the Sergeants, but they don't really understand them.