If they don't need four, then why do they have four?
insurance through multiple redundancy.
a four-engine plane can remain aloft safely with only two engines. not adviseable, since losing one more = crisis.
It's required per FAA regs that they have more power than they need.
The twin engine jets can actually take off on one.
Four engines looks cooler than two.
Redundancy makes for safer flying!
>>> If they don't need four, then why do they have four? <<<
1 So they can lose one.
2 Climb higher & climb faster
3 Can use lower power setting reducing stress on engines increasing life
When the 747 came out. Fan-Jet engines were new and not as reliable as now.