In the commercial airline industry, some days can involve some pretty rough times for customers and the airline staff often take the brunt of the feelings from the customers. By asking this question, your interviewer is looking to gauge your understanding of the potential downsides to a role in customer service with their airline, and that you've put thought into how you would handle these days. As you answer this question, be sure to highlight the importance of always maintaining a positive attitude no matter what is happening during your day. Also be sure that you don't sound like you are complaining about any days that you've had like this in the past, as that will reflect poorly on your ability to handle this aspect of the job. In the end, keep your response customer focused by highlighting your ability to work with customers in this mindset.