The Boeing 737: the original, the classic, the NG and the MAX – what’s the difference?



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The 737 was a big achievement for Boeing. In fact, it is the best-selling commercial jet to date. In production for over 50 years, it has been continually modified and updated through many variations – part of its success. This article examines the main differences between each 737 family: Original, Classic, Next Generation, and MAX.

Boeing 737 MAX Series
The Boeing 737 MAX series is the latest to join the long-standing family. Photo: Boeing

A long and successful story

The Boeing 737 was introduced in 1967 and has remained in flight and in production since. To date, 10,575 have been delivered (according to Boeing data in February 2020) and 15,115 have been ordered. This makes it the best-selling aircraft to date, but the Airbus A320 has now caught up with its orders.

Part of that success has been its well-designed design and constant evolution to meet airline demands. In the 1960s, the first 737 was designed to beat the competition of the time (mainly the Douglas DC-9, but also the BAC One Eleven and the Caravelle de Sud Aviation). As the 737 evolved into its variants, these improvements continued and maintained it as the first narrow-body choice for many airlines.

So what were the main differences for each series?

Pan Am 707
Boeing has had great success with the 707, and the 737 has benefited a lot. Photo: airandspace.si.edu via Wikimedia

The 737 Original – the 737-100 and the 200

One of the main features of the early 737s was, in fact, two engines. This was a driving motivation in the development of the 737. Previous Boeing planes, the 707 and 727, had both been very successful. But the market’s attention had shifted to a more economical dual-engine possibility.

Boeing got a head start on the competition by placing the 737’s two engines under the wing, rather than mounted at the rear of the fuselage. Critically, this allowed for a wider fuselage, giving the 737 additional passenger capacity (six instead of five), and allowed loading of standard freight containers. The simple conversion to the use of freight was popular with many airlines.

Boeing 737-100
The Boeing 737-100 first entered service in 1967. Photo: Boeing

Only 60 737-100 aircraft were sold, and it was quickly improved with the 737-200. This offered an elongated 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 higher fuel capacity and range.

Other changes have been made to meet airline demand. These included a Combi version for easy conversion to freight use, and the provision of an “unpaved strip kit” to allow landing on gravel runways.

737-200 with uncoated belt kit
Boeing’s unpaved strip kit has been made available for the 737-100 / 200 aircraft only. Photo: Biggerben via Wikimedia

The 737 Classic – the 737-300, 400 and 500

Production of the “Classic” series began with the 737-300 in 1984. The goal was a transformation focused on increased capacity and improved fuel efficiency. The family would be modified but would keep some commonalities (both in design and flight operation) with the previous models.

The main difference was the addition of new engines. The 737-300 uses CFM56 turbofan motors. This increased thrust (up to 23,500 lbf compared to 16,400 lbf for the Pratt & Whitney engines on the 737-200), but led to some design challenges. The 737’s larger engine diameter and low ground clearance meant they were placed in front of the wing.

737-300 southwest
The 737-300 was the best-selling of the original and classic series. Photo: Dylan Ashe via Wikimedia

The 737-300 offered a slight increase in capacity (up to a maximum of 149 against 136 for the 737-200), from an extension of the fuselage around the wing. Other structural improvements included:

  • Increased wingspan and extension of the wing tips, providing improved aerodynamics
  • Rear fin resignation
  • Several cabin improvements (based on features developed for the Boeing 757)

The 737-400 continued this expansion. Stretching the 737-300 to about three meters increased the capacity to 188. In contrast, the 737-500 was a smaller model. This returned to the size and capacity of the 737-200, but offered the design and efficiency improvements of the Classic series.

Bahamasair, 737-500
The latest member of the Classic series, the 737-500, offered a direct alternative to the aging 737-200s. Photo: BriYYZ via Wikimedia Commons

The 737 Next Generation – the 737-600, 700, 800 and 900

The Next Generation (NG) series was launched in 1993 (first flight in 1997). This was mainly due to growing competition from the Airbus A320 family and high fuel prices at the time.

The series offered several improvements over the conventional aircraft, including improved fuel efficiency, extended range and higher capacity variants (up to 215 passengers). Modifications to the aircraft included:

  • Improved CFM56-7 series engines with improved fuel efficiency
  • A redesigned wing, with an increased wingspan and surface area (and allowing for increased fuel capacity)
  • Improved digital cockpit
  • Interior cabin improvements including more storage space (with several updates based on 777 designs)
Interior of the 737NG
The revised cabin interior of the 737NG. Photo: Boeing

The 737-600 is the smallest in the family, with a capacity of 149 passengers. The 737-700 is stretched about 2.4 meters and also offered a convertible cargo option, the 737-700C.

The 737-800 is more elongated than the 737-700, making it a good replacement for the 737-400. It takes passenger capacity up to 189. This is further increased on the longest model – the 737-900ER, with capacity up to 220 (the 737-900 is limited to 189 due to a single set fewer exit doors).

The 737-800 became Boeing’s best-selling 737 model. Simple Flying examined this in detail, explaining how the compromise made it so successful. It offers a great combination of range and capacity, not the greater of the two, but a very versatile option for many airlines.

American Airlines 737-800 aircraft
The 737-800 has been very successful as a great all-round performer. Photo: Getty Images

The 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 again focuses on improving efficiency.

It uses new, more efficient CFM International LEAP engines and includes several aerodynamic modifications, including distinctive winglets.

Like the NG series, there are four MAX variants in different sizes. These generally offer increased passenger capacity and range compared to NG variants. Simple Flying took a closer look at these differences in a previous article.

737 MAX
The 737 MAX with LEAP engines and winglets. Photo: Getty Images.

The 737 MAX, of course, suffered from its grounding in 2019 following two crashes. It turned out to be popular, however, with 4,741 orders (based on Wikipedia order data).

This clearly shows its popularity and appeal to airlines. Since 2011 alone, it has already nearly matched 737 to 800 orders (and this has been on sale since 1993). If Boeing manages to overcome the problems, the 737 MAX could be a big hit.

The next 737?

While the MAX series problems and the aviation slowdown in 2020 may well change plans for new aircraft, Boeing already has plans for a new aircraft. This was originally planned by 2030.

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