Hands up now all those who bought a Prius, do you feel like a tit?
The biggest have in automotive history.... with the exception of the PT Cruiser (hey want an older looking new car... heres one we mangled earlier) you burn exactly how much less fuel a year... a thimble... well done
, unless you just bimble to shops it useless... I'm all for planet saving gadgets but don't put a pigs ear in a box and sell me a purse.
When you can do a X-country land and 're-fuel' at a remote airfeild- (an extension cord will do) then i'd be interested.
but why oh why put this technology into and airframe designed 50+ years ago. take advantage of the advances in composites and aerodynamics, build somethign really slippery, then you'd save a lot more power than dragging an in-effecient airframe through the sky.