In the design of human-machine interfaces and automation, an important question is how to obtain and validate a design that is capable of supporting the operator's understanding and situation awareness of the process under control. Whereas many research efforts address the question of 'what is the operator aware of?' - the awareness - only a few investigations focus on studying what the operator should be aware of in the first place, i.e., 'what is the situation?' In this paper we briefly discuss some of our research activities which aim at answering this second question, following an 'ecological approach' to interface design. The clever use of automation tools and novel visualizations will be presented that allows human operators working in aviation (pilots, air traffic controllers) in dealing with complex tasks. The airborne self-separation task will be discussed, as an example of showing how ecological interfaces can support pilots in their decision making.