The Boeing 737 Classic refers to the -300/-400/-500 series of the Boeing 737. It is the second-generation derivative of the 737, following the original -100/-200 models that began production in 1966. They are short- to medium-range, narrow-body jet airliners. Produced by Boeing Commercial Airplanes from 1984 to 2000, the 737 Classic includes three variants and can seat between 145 and 188 passengers. Improvements over the previous generation of 737 aircraft included CFM International CFM56 high-bypass-ratio turbofan engines, upgraded avionics, and increased passenger capacity (in the -300/-400 models).
The first model of the Classic series, the 737–300, entered service in 1984. It was followed by a stretched model, the 737-400, which entered service in 1988, followed by the shortened 737-500, the smallest variant in the classic series, in 1990. In total, 1,988 aircraft were delivered. The Classic series was introduced as the new generation of the 737, but following the introduction of the 737 Next Generation in the mid-1990s, was officially designated as the 737 Classic series.
The 737 has four different winglet types: 737-200 Mini-winglet, 737 Classic/NG Blended Winglet, 737 Split Scimitar Winglet, and 737 MAX Advanced Technology Winglet. The 737-200 Mini-winglets are part of the Quiet Wing Corp modification kit that received certification in 2005.
Blended winglets are in production on 737 NG aircraft and are available for retrofit on 737 Classic models. These winglets stand approximately 8 feet (2.4 m) tall and are installed at the wing tips. They help to reduce fuel burn (by reducing vortex drag), engine wear, and takeoff noise. Overall fuel efficiency improvement is up to five percent through the reduction of lift-induced drag.