Don't overthink this question - your response to this can be as simple as choosing to help someone cross the street because you noticed their hands were full and the light was changing. The main thing the interviewers are looking for here is a candidate that is customer-focused and can identify the little things that might make a customer's experience better and more memorable. They will have a series of questions and scenarios to identify your ability to jump into action when needed; in this question, they're looking for the intuitive side of airline stewards that will see that someone looks cold and come offer them a blanket.