The importance of redundancy and backup alternatives in any major project:<p>"It is worth remembering too, of course, that the F-35 enterprise almost had an alternative engine to the F135. However, the General Electric/Rolls-Royce F136 turbofan was deemed to be an unnecessary expense and was eventually canceled in 2011, when the project was over 80 percent complete. With the benefit of hindsight, it can well be imagined that an alternative source of engines would be very valuable right now."