Deedave one problem Sheffield had to start with was that single engined aircraft were not allowed to operate into there. This significantly reduced the amount of revenue they could recieve. Another problem was/is that Sheffield has a small runway, this means only small aircraft much like those that operate in to LCY can use the place. This coupled with the fact that Sheffield is towards the center of the country meant that there were already good surface transport links to the city to the ret of the country before you take into account any airports close by. The whole venture was a cock up all for a few extra hundred feet of runway. Manston on the otherhand has got a good length of runway and so there is always going to be the chance that a low cost will come in and make a go of things. Manston may have problems with catchment overlaps with the London airports but at least the infastructure at Manston is capable of supporting what the public wants. Sheffield was never allowed to.