The Vast amount of knowledge on the operation of long-haul jet aircraft will inevitably pass on to the short-haul jet; but it is felt that, in the take-off régime, further study must be done. A short-haul jet will probably average 8 to 12 take-offs a day—considerably more than a long-haul jet— and many of these take-offs will involve relatively minor airfields with short runways. In addition, on a world-wide basis, there is an increasing awareness of obstacles under the flight path. Roberts of North Central Airlines and Cooke of United Airlines have emphasised this aspect from the operator's point of view. As an example, calculation of a single point involving an obstacle limited take-off weight would take a pilot at least an hour. For efficient short-haul operation, this wastage of time is prohibitive.