Air traffic control was initially regarded primarily as a safety service, the constraints
of which in terms of cost and delays,;. which were in fact relatively minor - had to
be tolerated. It did not begin to be seen as a restrictive factor before the 1980s. Until
then, airports. has been regarded. as the main. bottleneck and it was thought that the
development of air transport was therefore only limited by the number of runways
which the environment would tolerate