David Nelson previews Delta Air Lines (DAL) earnings and discuss the broader airline sector. Nelson examines elevated fuel costs, softer passenger traffic, rising airfares, and airlines' efforts to maintain margins through premium seating and add-on fees. He also explains Delta's competitive advantages, including its refinery ownership, compares the outlook for competitors such as American Airlines (AAL), and discusses why investors will be focused on forward guidance and demand trends as earnings season gets underway.