I don't think that is what they mean to say. The slide on page 128 of http://aviationweek.typepad.com/files/mit_n3_final_presentation.pdf http://aviationweek.ty

I don't think that is what they mean to say. The slide on page 128 of http://aviationweek.typepad.com/files/mit_n3_final_presentation.pdf http://aviationweek.typepad.com/files/mit_n3_final_presentat... for instance breaks down the fuel savings by various changes: D8.1 configuration (double bubble) 49% Airframe Advanced Materials 8% High BPR Engines 4% .. and a long tail that might be 8% more for the engines. Now maybe the D8.1 configuration is only possible with impossible engines. I can not say.