In the global commercial aviation industry, profitability often looks complicated from an external perspective. Fuel prices can swing wildly, labor costs can rise, aircraft are expensive, and demand can change quickly with shifts in the economy. Nonetheless, beneath all of that complexity, there is one simple operating metric that helps explain whether an airline is actually making money on its routes. This is the gap between revenue per available seat mile (RASM) and cost per available seat mile (CASM). This is the most standard way that industry analysts estimate operating margins in the industry. This figure is essentially how much revenue an airline generates per available seat mile, compared with how much it costs to produce that seat mile.