The MD-80 versions have cockpit, avionics and aerodynamic upgrades along with the more powerful, more efficient and quieter JT8D-200 series engines, which are a significant upgrade over the smaller JT8D-15, -17, -11, and -9 series. The MD-80 series aircraft also have longer fuselages than their earlier DC-9 counterparts, as well as longer range. Some customers, such as American Airlines, still refer to the planes in fleet documentation as "Super 80". Comparable airliners to the MD-80 series include the Boeing 737-400 and Airbus A320.