The A320 is 37.6 m (123 ft) long and can accommodate 150 to 186 passengers. The 44.5 m (146 ft) A321 offers 185 to 230 seats.

The Airbus A321 is essentially a "stretched" version of the A320, designed to carry more passengers and cargo over similar distances. While both belong to the same A320ceo/neo family and share a common flight deck (allowing pilots to fly both with the same "Type Rating"), the A321 is approximately 23 feet (7 meters) longer. This extra length allows it to seat 185–240 passengers, compared to the 150–180 typical of the A320. To handle the increased weight, the A321 features a reinforced wing, a more powerful braking system, and specialized "double-slotted" flaps for better lift. In 2026, the A321neo (and its long-range variants like the LR and XLR) has become the dominant narrow-body aircraft for transatlantic and "long-thin" routes, effectively replacing the Boeing 757. For a passenger, the experience is nearly identical, though the A321 often feels slightly more stable in turbulence due to its increased length and weight, and it typically features more "Exit Row" seating options due to the additional emergency doors required for its higher capacity.