The most advanced OR work on aviation infrastructure
to date is undoubtedly associated with air traffic
flow management (ATFM). ATFM took on major
importance in the United States and Europe during
the 1980s, when rapid traffic growth made it necessary
to adopt a more strategic perspective on ATM.
Rather than addressing congestion through local measures
(e.g., by holding arriving aircraft in the airspace
near delay-prone airports) the goal of ATFM is to prevent
local system overloading by dynamically adjusting
the flows of aircraft on a national or regional
basis. It develops flow plans that attempt to dynamically
match traffic demand with available capacity
over longer time horizons, typically extending from
3–12 hours in the future. The prototypical application
of ATFM is in ground holding, i.e., in intentionally
delaying an aircraft’s takeoff for a specified amount
of time to avoid airborne delays and excessive controller
workload later on. Other ATFM tactics include
rerouting of aircraft and metering (controlling the rate)
of traffic flows through specified spatial boundaries
in airspace.
An important difference in the nature of the ATFM
problem in the United States and in Europe should
also be noted. In the United States, ATFM is primarily
driven by airport capacity constraints, whereas in
Europe en route airspace acts as the principal “bottleneck.”
Europe’s Central Flow Management Unit,
located in Brussels, currently determines (heuristically)
ground delays to ensure that no en route sector
capacity constraints are violated. This difference
may, however, become moot in the near future due
to continuing progress in increasing en route airspace
capacity in Europe.
OR model development related to ATFM can be
viewed as going through two distinct stages. The
first stage involved problem definition and development
of large-scale mathematical optimization models
of an aggregate scope. Attwool (1977) was the
first to cast ATFM issues in mathematical terms, while