Two actuaries are on a flight across the Atlantic in a 4 engine airplane. An hour into the flight the pilot announces that one of the engines has stopped and, while it’s not a threat to safety, it will slow them and delay the arrival time. So the actuaries, doing what they do, start calculating the ETA and one states, “that’s going to delay us an hour.” A while later the pilot comes on again and announces that a second engine went out so the ETA would be a bit later still. The actuaries start crunching numbers and determine they will be 2 hours late. Soon after the pilot comes on the PA again and announces that the third engine had also failed but the plane was engineered to fly on one engine and now they’d be even later. The actuaries start calculating again and determined that they would now be 3 hours late. After a period of time the pilot again makes an announcement but this time that they are on approach to landing. Well, thank heavens, said one of the actuaries, if that fourth engine went out we’d be up here all day.