Two Irishmen are flying home from London.
Shortly after taking off there is a big explosion and the pilot announces that one of the engines has gone and the flight will take 20 minutes longer. Not long afterwards the pilot announces that a second engine has failed and the flight time will longer still. Half an hour later the pilot speaks to the passenger again to say that they are now flying on one engine and gives an even later arrival time.
When the plane finally lands one Irishman turns to the other and remarks
"Just as well the fourth engine kept going or we'd have been up there all night."