Part of the reason we don't have as many 3 and 4 engine airliners anymore is ETOPS[1]. Modern turbine engines are so reliable, powerful, and efficient that ther

Part of the reason we don't have as many 3 and 4 engine airliners anymore is ETOPS[1]. Modern turbine engines are so reliable, powerful, and efficient that there's not as significant of a need for the additional redundancy provided by a third or fourth engine. --- [1] http://en.wikipedia.org/wiki/ETOPS http://en.wikipedia.org/wiki/ETOPS