Notwithstanding this complexity, flight schedule
design and variants of the problem have been of
interest to researchers for many years, with Simpson
(1966), Chan (1972), Soumis et al. (1980), and Etschmaier and Mathaisel (1984) describing early
work. Nonetheless, because of the inability of optimization
models to adequately capture the scope of
the design problem, the typical airline practice today
is to build flight schedules manually, with limited
optimization. With recent research advances, however,
this trend is reversing and optimization is beginning
to play a role.