Two statisticians were traveling in an airplane from Lisbon to Moscow. About an hour into the flight, the pilot announced that they had lost an engine, but don't worry, there are three left. However, instead of 5 hours it would take 7 hours to get to Moscow.
A little later, he announced that a second engine failed, and they still had two left, but it would take 10 hours to get to Moscow.
Somewhat later, the pilot again came on the intercom and announced that a third engine had died. Never fear, he announced, because the plane could fly on a single engine. However, it would now take 18 hours to get to Moscow.
At this point, one statistician turned to the other and said, "Gee, I hope we don't lose that last engine, or we'll be up here forever!"