Originally Posted by rickair7777

The A330 is a twin.

ETOPS (two engine over-water) flights are limited to something like three hours to a divert field (used to be two hours, but I think that changed for some operations).

Pacific long-haul operations require more than two engines for regulatory reasons, so the larger airplanes which are designed for that have four.

I think there are currently technical limitations on designing an engine large enough to only need two for a 747 or A380. Also the fan diameter, and hence landing gear length, would be very large which would create issues for ground handling (nobody could reach the fuselage).






Like I said before, I think the weight savings would be minimal. Carrying the spars all the way through might be a little more efficient, but engineers can do wonders with complex structures and arched structural objects (like a barrel-shaped wing-box) are inherently strong.