Ah, but don't forget that whilst the C does indeed have more fuel and goes further than the other variants - we couldn't possibly buy it because we tried to buy it once so a re-attack would make us look stupid and we would have to admit that wheel equipped naval jets were able to operate from surfaces other than boats. And in any case the A model is the Air Force variant so we need to buy that because we're an Air Force. Also it doesn't have a probe so we could spend more money fitting one, or fitting a boom to Voyager - whichever works out more expensive.