LogFAQs > #979070729

kirbymuncher posted...

Just speaking personally, I am definitely able to count the engines but until reading this post I never would have known this was a difference between the two

It's a large part of the reason 747s were used on almost every ocean crossing flight. At the time it was designed jet engines still had significant reliability problems so a two-engine plane was limited to staying within a certain distance (one hour flight time but don't quote me on that) of an airport in case an engine died. Two engine planes crossing the Atlantic had to go up and over across Iceland but the four engine 747 could cross direct due to the added engine redundancy. That regulation has long since been retired as jet engines improved.