Boeing 737 Classic

The Boeing 737 Classic refers to the -300/-400/-500 Boeing 737 series. It is the 737's second-generation derivative, following the original -100/-200 models. The 737 Classic models are short- to medium-range, narrow-body jet airliners that can seat between 145 and 188 passengers. Improvements over the previous 737 generation included CFM International CFM56 high-bypass-ratio turbofan engines and upgraded avionics.

The 737-300 entered service in 1984, followed by the 737-400 in 1988, and finally the smaller 737-500 in 1990.

Engines
Boeing selected the CFM56-3 to power the 737-300 variant. The 737 wings were closer to the ground than planes that had previously used the CFM56. This meant Boeing had to modify the engine by reducing the fan diameter in order to reduce the bypass ratio and by moving the engine accessory gearbox from the 6 o'clock position to the 9 o'clock position. Moving the gearbox gave the engine nacelle its distinctive flat-bottomed shape, often nicknamed the "hamster pouch".

Accidents and incidents
As of December 2017, 62 hull losses of Boeing 737 Classic series aircraft have occurred, with a total of 1,176 fatalities. According to a Boeing analysis on commercial jet airplane accidents from 1959-2013, the classic series has a hull loss rate of 0.54 per million departures versus 0.27 for the Next Generation series and 1.75 for the original series.