Lessons learned from manual systems: designing information systems based on the situational theory of agency - Information Systems Foundations: Constructing and Criticising - page 171

The activity of landing a flight begins with a printed-paper flight strip containing basic
flight plan information. This strip is generated by computer or can be handwritten in
the absence of a working computer system. Figure 14.2 shows a typical flight strip.
Figure 14.2. A flight strip describing Air France Flight 540 (Mackay, 1998,
p. 322).
As an aircraft approaches an airport, a flight controller takes over control of its landing.
When a new strip is generated, the controller's first task is to remove it from the printer
and insert it into a strip holder. Strips are continually picked up and put down, reordered,
grouped, offset, moved into columns, arranged and rearranged on the controller's table
to denote different traffic conditions. The placement of the strips provides the controllers
with information regarding action additional to that written on the strips. As the landing
progresses, the flight passes from one controller to another by physical handover of the
flight strip that, by its nature, is palpable for both controllers. Often controllers are side
by side thus facilitating handover to another sector by structuring the area to help the
activity.
Once a controller takes control of a flight strip, he gradually adds information to the
typed strip (as seen in Figure 14.3). The markings allow controllers to look at a group
of flight strips and quickly select the ones coming under their control and other inform-
ation about how the activity is progressing. The layout of strips also gives a controller
an immediate appreciation of the control environment (involving many flights) thus
helping the controller to select the next action.
Figure 14.3. The strips being manipulated by an operator.
Each strip represents the activity of landing a specific flight and contains information
important to landing the plane, not directly relating to the plane itself. In this way, the
information on a strip is not tied to any specific object. Neither does each strip contain