Although Gent and Van (1995) did not find that pilots reported a loss of situation awareness with such a gating option, it is important to realize that self-report of awareness will not necessarily be the same as actual awareness. The second concern is the possibility that designers may create a system in which the message is automatically loaded into the flight management system prior to a pilot's decision and the pilot would simply have the authority to activate it. It appears that this further removal of the pilot from the control loop would be a clear invitation to complacency.
Given possibilities envisioned by the different levels of gating, it is feasible that a system could be designed that allows alternative gating modes. Such a system will invite confusion: a pilot, for example, may assume that a message was automatically loaded into the flight management system (high automation, low gating), when in fact it was not.
In conclusion, the introduction of data link has profound implications for workload, for communications, and indeed for the overall structure of the national airspace system, characterized by the relationship between pilots, controllers, dispatchers, and automation. With modest goals, it is possible to envision a system that is designed primarily to provide a visual record of material transmitted by conventional voice channels. At the other extreme, it is possible to envision a scenario in which both human elements, on the ground and in the air, are substantially removed from the control loop, while control is exercised between computers on the ground and in the air. Although planners do not currently intend such a scenario, the possibility nevertheless exists that levels of automatic control and gating could be implemented that approximate this kind of interaction.