When they talk `efficiency` they should clearly state what components are factored in. They should also clearly state what is it compared to. If Boeing claims that their 787 is 20% more efficient, we need to know which version of 787 they mean. And we need to know what is this 20 % gain weighed against. Is it average statistics against various manufacturers in similar segment or a specific airplane with similar size and passenger capacity, or other criteria are applied?! Another question- how much of the gain is attributed to Boeing `( non-engine related) input and how much is attributed to more efficient engines supplied by other companies, thus also available to be installed on updated or revamped competitors ` planes.
Fuel efficiency is not enough. We need to factor in the PRICE of the airplane, parts availability, service intervals for various components, component price and parts replacement cycle. We need to factor in airplane complexity ( adds service costs)and reliability( adds delays), which can clearly add to unpredictable costs throughout the life cycle.
I think Boeing went the wrong direction by bleeding away the hardcore expertise on various know-how components allowing Fuji Heavy and Mitsubishi heavy gain expertise not only for their upcoming MRJ but for the future far beyond that. Boeing`s desperation to avoid high precision complex engineering( characteristic for the whole US prec. manuf. sector) and resort to penny pinching is biting back . Personally I think Airbus( unfortunately) is going to win the battle, as there are no signs in Europe of dwindling precision movement industries, be it industrial robots, car platforms or related industries. My 2 cents.