Scheduling through hubs
Other things being equal, concentration of flight activity at certain airports at certain times of day, increases the danger of collisions, both in the air and on the ground, as compared with spreading the same level of activity across a number of airports and across the day. To some extent there is a compensating factor here, insofar as connecting flights tend to reduce conflicting movements between arriving and departing aircraft. But most aviation accidents occur in landing/take-off or in climb/descent and, to the extent that hub and spoke operations reduce average sector lengths and encourage multi-sector routeings against direct non-stop flights, the development is not entirely conducive to flight safety. Flight safety records indicate that the risk to passengers on a non-stop flight is virtually independent of its length. On that basis, flying from A to B via C, which entails two flights, may be considered twice as dangerous as flying from A to B non-stop. However, it is by no means necessarily the case that hub and spokes systems, once fully developed, will result in a reduction in nonstop travel. Experience in the deregulated US domestic market has been that connecting passengers as a percentage of total passengers has increased only marginally since 1978 (Boeing Commercial Airplane Company, 1986). The proportion of passengers changing planes in hub and spokes networks is only fractionally greater than it was in linear networks before deregulation.