Delta utilizes the STAR behavior type interview. STAR stands for Situation, Task, Action, and Result. The interview is typically conducted by a panel of 2 or 3 managers, and they take turns asking the questions. There are categories of behaviors, and within each category is a set of questions. The panel can ask their choice from the set of questions, and the answers should be provided in brief detail: 1-2 sentences for the situation, 1-2 sentences for the tasks at hand, etc. Always make sure you specify the result.
Don't be afraid of the interviewers. They are looking to see who you are - they aren't trying to weed you out, they are seeing how you would fit in. Have a rapport with them - you'll be spending a lot of time working with them one day :)