The airline sector experienced a significant downturn after major carriers issued cautious full-year profit guidance. American Airlines stock fell after the company's full-year 2026 adjusted EPS forecast came in significantly below market expectations, implying a potential net loss for the year. Southwest Airlines also lowered its earnings outlook. The primary driver for the weakened forecasts is a substantial increase in jet fuel costs, which is overshadowing record revenue figures and raising concerns about future profitability for the industry.