A four-engined airliner was flying along when the captain announced "sorry folks, we have an engine failure; don't worry, there are 3 left but our trip will be a little longer than scheduled".
The passengers were a little concerned initially but soon settled down.
A while later, the captain comes on again and says "sorry folks, another engine has failed...again, no problems because these things are designed to handle such occurrences, but our trip will now take an extra hour."
Then lo and behold, after another few minutes, the captain announces "Sorry ladies and gentlemen, number 3 engine has just failed. Now don't worry because we can fly quite well on only one engine, but now it's going to take us just that bit longer to reach the destination."
The passengers are now a bit concerned, and Paddy turns to Fergus and says "Begorrah, I hope the fourth engine doesn't fail, otherwise we'll be up here all day!"
Boom boom