a man is sitting in an airliner, which is  about to take off when another man with a labrador retriever occupies the 2 empty seats beside him.  the lab is situated 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 Sniffer, he's a sniffing dog, the best there is; i'll show you one we take off when i put him to work.
 
the plan takes off and the handler says to the man "watch this" he tells the dog " sniffer, search."  sniffer jumps down, walks along the aisle, and sits next to a women for a few seconds.
 
when he returns to its seat and puts out one paw on the handlers arm.  He says " good boy".
The airline rep turns to the man and say that women is in posession of marijuana, so i am marking down her seat number so that when we land the police can apprehend her.
 
Fantastic replies the man  So again the dog does to sniff.  The lab sniffs and sits next to a man for a few seconds, comes back and and places to paw on the handlers arm.  The airline rep replies" that  man is carrying cocaine, so again I'm making a note of this and his seat number.
 
so the handler sends the dog out for a third time.  He sits down next to someone for a few seconds.  he then comes racing back, jumps up onto the seat, and poops all over the seat.  The man is really grossed out by the behavior from the supposedly well trained sniffing dog and asks " What's going on?"
 
The handler nervously replies, " He just found a bomb!"