Haughtney - I am not denying the central role of new technologies (obviously these are critical) but my point is that technology alone will not fix everything. As energy consumers, we will need to modify our own attitudes and practices. So what is the answer? There is no single answer - it is like winning a world war; it needs the combined resources of everyone over a long and difficult period. The detail of jet fuel substitutes is but one of many highly complex technical aspects. The overall reduction of our fossil fuel addiction is a huge challenge. The good news is that at least these things are being seriously discussed in the mainsteam; unthinkable a few years ago. It is a start. Oh, and no need to make caustic remarks to someone just because their opinion differs from yours!

James, I agree with you to a certain extent, but I have to reiterate that aviation emissions are a mere drop in the ocean when you compare them to the power generation industry, motor vehicles, domestic housing and international shipping.
Of that group of four, the two most polluting (and by pollution I refer to air quality and inefficiency NOT CO2) are certainly motor vehicles and power generation. These two industries already have at their disposal technologies that could effectively halve their environmental impact, however for many, it is far easier to point the finger at perceived luxuries aka "air travel" than it is to address the issues surrounding options such as nuclear power generation (take a look at how the French do it), and the emerging hydrogen fuel cell vehicles.
Technology, rather than banging on about "changing our ways:ugh: " is the way forward.

How about Extra Virgin Olive Oil...?
More expensive...?
Nice to know for catering salads, just drip the tanks...
Could possibly consider production of by-products such as mayonnaise...?
Aeronautical engineering and culinary arts mix quite well.