The Boeing 737-800 is a narrow-body airliner and a variant of the 737 Next Generation series. This variant, like other 737's in the Next Generation series, features upgraded engines and overall improvements however it's fuselage is almost exactly the same of the Boeing 737-400 making it possible for it to be a like-for-like replacement for that variant of the Classic series. The (WL) designation stands for Winglets which were not standard on initial models but introduced on later models as standard or retrofits. The 737-800 is the second longest variant but is the most popular variant of the Next Generations series. The 737-800, along with the it's -700 sister variant, have become the backbone of narrow-body fleets of airlines around the world. The 737-800 typically flies short to medium haul flights that have high demand and has a typical seating capacity of 160 seats in a two class configuration making it a large size plane in it's class.