A man is sitting in a plane which is about to takeoff when another man with a dog occupies the empty seats alongside. The dog is sat in the middle, and the first man is looking quizzically at the dog when the second man explains that they work for the airline. The airline rep said "Don't mind Rover, he is a sniffer dog, the best there is, I'll show you once we get airborne and I set him to work."
The plane takes off and levels out when the handler says to the first man, "Watch this." He tells the dog "Rover, search." The dog jumps down, walks along the aisle and sits next to a woman for a few seconds. It then returns to its seat and puts one paw on the handler's arm. He says "Good boy."
He turns to the first man and says, "That woman is in possession of marijuana, so I'm making a note of this, and the seat number, for the police who will apprehend her on arrival." "Fantastic!" replies the first man.
Once again he sends the dog to search the aisles. The dog sniffs about, sits down beside a man for a few seconds, returns to its seat and places both paws on the handler's arm. The airline rep says, "That man is carrying cocaine, so again, I'm making a note of this, and the seat number." "I like it!" says the first man.
Once again he sends the dog to search the aisles. Rover goes up and down the plane aisle and after a while sits down next to someone, and then comes racing back and jumps up onto the seat and craps all over the place.
The first man is surprised and disgusted by this, and asks "What the bloody hell is going on?"
The handler nervously replies "He just found a bomb!