The first condition for successful human factors contributions to air traffic control is acknowledgement that human factors as a discipline has a role in air traffic control. This is a necessary but not a sufficient condition, for it has to be accompanied by a willingness to act on human factors recommendations. Attitudes towards human factors are generally more supportive now than they formerly were, and scepticism and indifference are more common than outright hostility. The burden of proof has now switched from gaining recognition for human factors to delivering what it has promised. As a discipline, it has been lax in educating others about its roles, recommendations and achievements. Many who would confine its contributions to the later stages of system evolution have never been informed about its contributions at earlier stages. Contributions draw on basic human factors data and procedures (Wickens, 1992; Sanders and McCormick, 1993).