Southwest Airlines "Silver One"Southwest Airlines 737 airplane model. Boeing announced it was developing the 737 300 in March 1981. This new variant started off as a simple stretch over the 737 200 but Boeing decided to adopt the CFM International CFM56 high bypass turbofan (jointly developed by General Electric and SNECMA) to reduce fuel consumption and comply with the then proposed International Civil Aviation Organization Stage 3 noise limits. The 737 300 flew for the first time