STAC stated that an SST would have economic performance similar to existing subsonic types.[6] A significant problem is that lift is not generated the same way at supersonic and subsonic speeds, with the lift-to-drag ratio for supersonic designs being about half that of subsonic designs.[14] This means the aircraft would have to use more power than a subsonic design of the same size. But although they would burn more fuel in cruise, they would be able to fly more sorties in a given period of time, so fewer aircraft would be needed to service a particular route. This would remain economically advantageous as long as fuel represented a small percentage of operational costs, as it did at the time.[6]