Not sure if this is a good title and I have had to clean it up a bit, so here we go.
A man gets on to and airplane and sits in his seat next to the window, another man with a dog boards the plane and sits in the seat next to him.
The first man says to the second one, "I didn't know they allowed dogs on airplanes" the second man explained that he was a drugs enforcement officer.
Any way the plane took off and the second man said to the first "watch this the dog is going to work now". The dog walked up and down, then sat next to a woman for a few seconds, then returned to his owner and put a paw on his arm.
The second man said " ah, that woman is carrying marijuana, I'II take a note of her seat and we will arrest her when we land."
Then the dog went off again, it then sat next to a man for a few seconds then return and put both paws on his owners arm. The second man said "that's good that passenger is carrying cocaine, I will make a note of his seat number and arrest him when we land".
The dog went off to work again, after a few seconds the dog returned very excited and began to poo all over the floor. The first man started to complain to the second one about the mess and the smell.
The second man looked at the first man and said "that's bad, that's very bad" the first man looked at him blankly, then the second said "he's found a bomb".