I am posting this here so that hopefully it won't start an A vs B like I know it would in the civil aviation forum.
Boeing says, "The Boeing 757-300 has the lowest seat mile operating cost of any single-aisle airplane on the market, and a lower cost per trip than any twin-aisle airplane."
Airbus says, "The A321 is the largest member of the A320 Family. It offers the best seat-mile costs of any single-aisle aircraft and is even on a par with widebody efficiency, bringing a new dimension to profitability."
Someone has to be wrong here. Which aircraft is the most efficient? B753 or A321?