The 737 has been a great success story for Boeing. In fact, it has been the best-selling commercial jet to date. In production for more than 50 years, it has been continuously modified and updated through many variants – part of its success story. This article analyzes the main differences in each 737 family – Original, Classic, Next Generation and MAX.
A long history of success
The Boeing 737 was launched in 1967 and has been flying and in production ever since. To date, 10,575 have been delivered (according to Boeing data for February 2020), and 15,115 have been ordered. This makes it the best-selling aircraft to date, but the Airbus A320 is now high on orders.
Part of that success has been its well-designed design and constant evolution to meet the demands of airlines. In the 1960s, the first 737 was designed to beat the competition of the time (mainly the Douglas DC-9, but also the Sud Aviation BAC One Eleven and Caravelle). As the 737 went through its variants, these improvements continued and maintained it as the best choice of narrow body for many airlines.
So, what were the main differences of each series?
The Original 737 – the 737-100 and the 200
One of the main characteristics of the first 737s was, in fact, two engines. This was a driving motivation in the development of the 737. The previous Boeing aircraft, the 707 and the 727, were very successful. But the market’s attention has shifted to a more economical two-engine option.
Boeing came out ahead of the competition by placing the 737’s two engines under the wing, rather than mounted on the rear of the fuselage. Critically, this allowed for a wider fuselage, giving the 737 extra passenger capacity (six as opposed to five), and allowed standard cargo containers to be loaded. Simple conversion to freight use was popular with many airlines.
Only 60 737-100 aircraft were sold, and it was soon improved with the 737-200. This offered an extended fuselage, initially requested by United Airlines, and proved to be very popular (with 1,095 sales). There was also an Advanced version, with improved aerodynamics, more powerful engines and greater capacity and fuel range.
Other changes were made to meet the demand of airlines. This included a Combi version for easy conversion for freight use and the provision of an ‘Unpaved Strip Kit’ to allow landing on gravel runways.
The 737 Classic – the 737-300, 400 and 500
Production of the ‘Classic’ series started with the 737-300 in 1984. The goal was a transformation focused on increasing capacity and improving fuel efficiency. The family would be modified, but would maintain the similarity (both in the design and in the flight operation) with the previous models.
The main difference was adding new engines. The 737-300 uses CFM56 turbofan engines. That boost has increased (up to 23,500 lbf compared to 16,400 lbf for the Pratt & Whitney engines on the 737-200), but has led to some design challenges. The larger diameter of the engine and the low ground clearance of the 737 means that they were placed in front of the wing.
The 737-300 offered a small increase in capacity (up to a maximum of 149 compared to 136 for the 737-200), from an extension of the fuselage around the wing. Other structural improvements include:
- An increase in the wing wingspan and extension, offering improved aerodynamics
- Tail redesign
- Various cabin improvements (based on features developed for the Boeing 757)
The 737-400 continued this expansion. Stretching the 737-300 by about three meters increased the capacity to 188. In contrast, the 737-500 was a smaller model. This went back to the size and capacity of the 737-200, but offered improvements in the design and efficiency of the Classic series.
The 737 Next Generation – the 737-600, 700, 800 and 900
The Next Generation (NG) series was launched in 1993 (flying for the first time in 1997). This happened mainly to face the growing competition from the Airbus A320 family and the high fuel prices at the time.
The series offered several improvements over Classic aircraft, including improved fuel efficiency, extended range and larger capacity variants (up to 215 passengers). Aircraft changes included:
- Updated CFM56-7 series engines with improved fuel efficiency
- A redesigned wing, with increased breadth and area (and allowing greater fuel capacity)
- Enhanced digital cockpit
- Improvements to the internal cabin, including increased storage space (with several updates based on 777 designs)
The 737-600 is the smallest in the family, with a capacity for 149 passengers. The 737-700 is stretched by about 2.4 meters and also offered a convertible cargo option, the 737-700C.
The 737-800 is more elongated than the 737-700, which makes it a good replacement for the 737-400. It takes passenger capacity up to 189. This is further increased in the longest model – the 737-900ER, with a capacity of up to 220 (the 737-900 is limited to 189 due to having only one set of exit doors less) .
The 737-800 became Boeing’s best-selling 737 model. Simple Flying analyzed this in detail, discussing how the engagement made it a success. It offers an excellent combination of range and capacity, not the larger of the two, but a very versatile option for many airlines.
737 MAX Series
The fourth generation of the 737 family was launched in 2011. The 737 MAX series competes with the A320neo family (launched in 2010) and once again focuses on improving efficiency.
It uses new and more efficient CFM International LEAP engines and includes several aerodynamic modifications, including distinct winglets.
Like the NG series, there are four MAX variants of different sizes. They generally offer greater passenger capacity and range over NG variants. Simple Flying examined these differences more closely in a previous article.
The 737 MAX, of course, suffered from stranding in 2019 after two accidents. It still proved popular, with 4,741 orders (based on Wikipedia’s order data).
This shows its popularity and appeal to airlines as well. Since 2011, he has almost fulfilled orders for 737-800 (and has been on sale since 1993). If Boeing can overcome the problems, the 737 MAX could be a great success.
The next 737?
While the problems with the MAX series and the aviation slowdown in 2020 could change plans for new aircraft, Boeing already has plans for a new aircraft. This was initially planned for 2030.
It would probably be a composite fuselage construction, offering a light and economical construction. Potential modifications also include an electric cross section, offering a wider cabin with the possibility of two aisles. Extending the cabin was how the 737 Original got its lead, so it will be interesting to see if it will happen again.[iticalcross-sectionofferingawidercabinwiththepossibilityoftwoaislesWideningthecabinwashowthe737Originalgotitsleadsoitwillbeinterestingtofollowwhetherthishappensagain[iticalcross-sectionofferingawidercabinwiththepossibilityoftwoaislesWideningthecabinwashowthe737Originalgotitsleadsoitwillbeinterestingtofollowwhetherthishappensagain