Here's a fairly detailed article on the issue: https://www.boeing.com/commercial/aeromagazine/articles/qtr_4_07/article_02_1.html https://www.boeing.com/commer

Here's a fairly detailed article on the issue: https://www.boeing.com/commercial/aeromagazine/articles/qtr_4_07/article_02_1.html https://www.boeing.com/commercial/aeromagazine/articles/qtr_... The main points are increased efficiency and decreased maintenance costs.