The Boeing 737 Classic and Boeing 737 Next Generation (NG) are two distinct series within the 737 family, each with its own set of improvements and changes. Here are the primary differences between them:

1. Design and Structure:

   • 737 Classic: This series includes the 737-300, 737-400, and 737-500 models. It was produced from the 1980s to the late 1990s. The Classic series introduced a wider and more spacious cabin compared to earlier models and featured CFM56-3 engines.
   • 737 Next Generation (NG): This series includes the 737-600, 737-700, 737-800, and 737-900 models. Introduced in the late 1990s, the NG series features a redesigned wing with a larger span and area, which improves aerodynamics and fuel efficiency. The NG series also uses CFM56-7 engines, which are more powerful and efficient than the engines used in the Classic series.

2. Performance and Efficiency:

   • Engines: The NG series uses more advanced CFM56-7 engines, which provide better fuel efficiency, reduced noise, and lower emissions compared to the CFM56-3 engines on the Classic series.
   • Range and Capacity: The NG series offers increased range and capacity, allowing airlines to operate longer routes and carry more passengers. For instance, the 737-800 in the NG series has a higher seating capacity and longer range than the 737-400 in the Classic series.

3. Avionics and Technology:

   • Cockpit: The NG series features an updated "glass cockpit" with modern avionics, including larger displays and more advanced flight management systems. This provides pilots with better situational awareness and improves operational efficiency.
   • Systems: The NG series incorporates more advanced systems, including improved navigation and communication systems, enhancing safety and reliability.

4. Interior and Comfort:

   • Cabin Design: The NG series offers improved cabin design with options for modern in-flight entertainment systems, better lighting, and more comfortable seating arrangements. These enhancements contribute to a better passenger experience.

In summary, the Boeing 737 Next Generation series introduced significant improvements over the Classic series in terms of design, performance, efficiency, technology, and passenger comfort. These advancements have made the NG series a popular choice for airlines worldwide.