4 Engine Shutdown Frequency
Maths,chaps! Although it is true that the probability of a shutdown on a four-jet is double that of a twin, the probability of two shutdowns on the same. day is much smaller. If you don't believe me consider the case of (say) a B52 How often do they lose four engines at the same time?! Whether the four jet is safer or not depends (of course) on whether it will fly on two engines and for how long.