BA's failure to simplify its complex, hierarchical organisation to enable it to reduce its overheads has been the main reason that has until now prevented the airline from achieving a cost structure that would make its Gatwick operation profitable. This situation has been further compounded by the fact that the company enjoys fewer economies of scale at Gatwick compared with Heathrow because the firm's operation at the former airport is smaller than the one at the latter. As a general rule, on average, a full-service scheduled operation at Gatwick with a fare structure that is identical to a similar operation at Heathrow produces a 10% lower load factor. It also generates a 20% lower revenue and results in an up to 25% lower yield. Although the growing presence of aggressive low-cost, "no frills" airlines on an ever-increasing number of UK domestic and European routes since the late 1990s has rendered this rule largely invalid for short to medium haul operations, it is still valid for most long haul operations where the competition from low-cost airlines is still in its infancy. Heathrow's and Gatwick's respective geographic location as well as the number of people living within each airport's catchment area accounts for this difference in load factors, revenues and yields. The former has a bigger catchment area than the latter because more people live north of the Thames than south of it. Heathrow's catchment area includes about three-quarters of London's population and roughly two-thirds of the population in the whole of Southeast England. London is where most of the demand for air travel in the Southeast originates. This means that 5.6mn people in London live in Heathrow's catchment area as opposed to 1.9mn in Gatwick's catchment area (out of an estimated total Greater London population of 7.5mn). The comparable figures for the Southeast are: 6.7mn people in Heathrow's catchment area as opposed to 3.3mn in Gatwick's catchment area (out of an estimated total population of 10mn). This is of particular significance for the premium travel market as Heathrow's larger catchment area means that it is able to offer more frequent flights to a greater number of destinations with more conveniently timed connections. This, in turn, helps attract a greater number of business travellers who generally tend to be the airlines' most profitable customers. It also means that there are four to five business travellers in Heathrow's catchment area for every business traveller in Gatwick's catchment area. On the other hand, the differing sizes of Heathrow's and Gatwick's catchment areas are far less significant for non-premium travel as many people are prepared to travel to an airport outside their catchment area to take advantage of a cheaper flight.