With almost 15,000 aircraft ordered, and with continued production over more than five decades, the Boeing 737 family is, together with the Airbus A320 family, one of the two most successful airliners in the history of commercial aviation.
Since the very first 737-100 flew for the first time in 1967, Boeing has introduced over ten different variants through four different generations of this iconic narrow-body aircraft. Today, only the latest generation – the B737 MAX – remains in production as a commercial airliner.
That said, thousands of airframes of its predecessor – the B737 Next Generation – remain in service, and so do some 737s from the Original and Classic generations.
Continue reading to learn more about all of the different 737 variants that Boeing has offered. I’ll take each variant by generation in turn, but first I’ll provide some context on the origin of this aircraft and the number of orders that Boeing has received for each variant.
A Brief Look at Boeing 737’s Origin
In the 1960s Boeing was looking to introduce a short-haul commercial aircraft, smaller than the 707, to complement the 727. Other aircraft manufacturers were ahead of the game and Boeing was facing increasing competition from the Douglas DC-9 and the British Aircraft Corporation’s BAC 1-11.
To save production time, and to get the 737 to the market as quickly as possible, Boeing used the same upper lobe fuselage design as the 707 and the 727. This allowed the 737 to have six-abreast seating which was a key selling point against the DC-9’s five-abreast seating.
The number of seats in the 737 also was increased compared to rear-mounted twin or tri-jets by mounting the engines under the wing. The 737 engine configuration also simplified maintenance as the engines were closer to the ground compared to the rival tri-jets.
Boeing initiated the 737 program in February 1965 with Lufthansa as the launch customer.
Boeing 737 Orders and Deliveries
I looked at Boeing’s official data as of the end of June 2022 to investigate how many 737s have been ordered and delivered for each variant. This is what I found:
* For the 737MAX I had to interpret the Boeing data to exclude orders canceled after the 2018/2019 MAX air crashes (more on this later). So, the 737MAX ‘deliveries’ in the graph above are the sum of delivered aircraft and unfulfilled orders to provide a ‘like-for-like’ comparison with other variants.
The graph above shows that the 737-800 and the 737 MAX are the two most successful 737 variants. If we group the number of deliveries by 737 generation, we see that the Next Generation is the most successful of the four 737 generations to date.
Also, for context, let’s look at the delivery years and some other key variables for each variant:
| 737 Variant | Delivery Period | Delivery Period (no. of years) | First Operator | Length/m |
| 737-100 | 1967 – 1973 | 7 | Lufthansa | 28.65 |
| 737-200 | 1967 – 1988 | 22 | United Airlines | 30.53 |
| 737-300 | 1984 – 1999 | 16 | Southwest Airlines | 33.40 |
| 737-400 | 1988 – 2000 | 13 | PACE Airlines | 36.50 |
| 737-500 | 1990 – 1999 | 10 | Southwest Airlines | 31.10 |
| 737-600 | 1998 – 2006 | 9 | Scandinavian Airlines | 31.20 |
| 737-700 | 1997 – 2017 | 21 | Southwest Airlines | 33.60 |
| 737-800 | 1998 – 2020 | 23 | TUIFly | 39.50 |
| 737-900 | 2001 – 2005 | 5 | Alaska Airlines | 42.14 |
| 737-900ER | 2007 – 2019 | 13 | Alaska Airlines | 42.14 |
| 737 MAX 7 | 2021 – | N/A | Southwest Airlines | 35.56 |
| 737 MAX 8 | 2017- | N/A | Malindo Air (Lion Air) | 39.52 |
| B37 MAX 200 | 2021 – | N/A | Ryanair | 39.52 |
| 737 MAX 9 | 2018 – | N/A | Thai Lion Air | 42.16 |
| 737 MAX 10 | 2023 (est.) – | N/A | United Airlines | 43.80 |
Types of Boeing 737: 10+ Variants Across Four Generations
With the basics out of the way, let’s look at each of the different 737 variants one by one.
Boeing 737 Original
The first generation of the 737, now known as the Original generation, comprises two main variants – the 737-100 and the 737-200. More than one thousand 737 Originals were delivered by Boeing.
737-100
At just 28.7m long, the 737-100 is the shortest of all the 737 aircraft offering only around 85 seats in a typical 2-class cabin. The 737-100 is also the 737 variant with the shortest wingspan at 28.3m. These dimensions gave the 737-100 its characteristic short and stubby appearance, and these early 737s were called the ‘square airplane’ because they were as long as they were wide.
The 737-100 flew commercially for the first time in 1967 with Lufthansa. The improved 737-200 variant was introduced almost immediately after and so only thirty 737-100s were built.
Twenty-two 737-100s were delivered to Lufthansa, five to Malaysia-Singapore Airlines, and two to Avianca. All of these original aircraft subsequently changed hands and sadly, none remain in service today. All have been scrapped or written off, apart from one that is on display in the Museum of Flight in Seattle. This is the 737-100 that served NASA.
737-200
The second variant of the 737, the 737-200, entered into service with United Airlines almost concurrently with the first 737-100 delivery.
United Airlines wanted an aircraft with a slightly higher seat capacity than the B737-100, so Boeing stretched the 737 fuselage by almost 2m to create the B737-200. The 737-200 allowed around 102 seats in a typical 2-class configuration.
In 1971, an improved version of the variant, the 737-200 ‘Advanced’ started service with Japan’s ANA. The 737-200 ‘Advanced’ helped sustain 737 sales with its improved aerodynamics, automatic wheel brakes, more powerful engines, and more fuel capacity, permitting an increased payload and longer range compared to the original 737-100s and 737-200s.
Production of the 737-200 ended in 1988, and over the roughly twenty years that the 737-200 was in production, more than one thousand airframes were produced and delivered to customers.
Less than sixty 737-200s remain in service today. Most notable of these are the 737-200s that are operated by airlines such as Air Inuit which provides flights to, from, and around remote areas of Northern Canada, proving just how reliable and suited for rugged conditions this airplane is. Air Zimbabwe still operates a 737-200 too, and a number of others are in operation with various air forces around the world.
Boeing 737 Classic
The next development of the B737, known as the Classic generation, comprises three more fuel-efficient variants with differing capacities and ranges: the 737-300, the 737-400, and the 737-500. Almost two thousand 737 Classics were delivered by Boeing.
737-300
The first commercial flight of the 737-300 was in 1984 with Southwest Airlines and over one thousand 737-300s were delivered by Boeing over its 16-year production period.
The 737-300 was originally conceived as a way to increase capacity (126 seats in a typical 2-class configuration) and range, whilst retaining commonality with previous 737 variants.
The 737-300 was fitted with distinctive, non-circular CFM International turbofan engines. Increased passenger capacity was achieved by extending the fuselage around the wing by 2.87m, and the passenger cabin included improvements similar to those developed for the 757.
737-400
The 737-400 was first delivered in 1988 and offered a further fuselage stretch and increased seating capacity (147 seats in a typical 2-class configuration).
After 13 years of deliveries, the last two 737-400s were delivered to CSA Czech Airlines in 2000. Some 737-400s were converted to freighters and these became known as the 737-400SF.
737-500
The 737-500 had a short fuselage, similar in length to the 737-200 (just 0.48m longer than the 737-200), and its first commercial flight was with Southwest Airlines in 1990. It has a typical 2-class seating capacity of 110.
The increased range of the 737-500 allowed longer routes to operate with fewer passengers more economically than the 737-300.
Boeing 737 Next Generation
Boeing launched the Next Generation (or Next Gen or NG) development of the B737 to try and stave off the increasing competition from the Airbus A320. Fuel efficiency was a key objective of the Boeing designers at the time to address the A320 competition issue and to address concerns over increasing oil prices.
The 737NG was a significant update to the 737, with a new airframe and wing designs, and a glass cockpit.
This generation comprises of four main variants – the 737-600, the 737-700 (and 737-700ER), the 737-800, and the 737-900 (and 737-900ER). Almost seven thousand 737NG aircraft were delivered by Boeing.
737-600
The 737-600 is the smallest 737NG variant with a typical two-class capacity of just 108 seats and was designed as a replacement for the 737-500, and as a competitor for the A318.
737-700
The 737-700 is 2.4m longer than the 737-600, taking its typical 2-class capacity to 126 seats. The 737-700 was the first 737NG variant to roll off the production line in 1997.
737-800
The 737-800 is almost 6m longer than the 737-700 leading to a significantly increased seating capacity (162 seats in a typical 2-class configuration). To date, the 737-800 is the most-delivered 737 variant with more than 5,400 aircraft rolling off Boeing’s production line.
737-900
A further fuselage stretch came with the 737-900 and 737-900ER, and with the fuselage more than 42m long, a typical 2-class capacity of 178 seats was achievable.
Most of the 737-900 series deliveries were for the 737-900ER. More than five hundred 737-900ERs were delivered compared to only fifty-two 737-900s.
Boeing 737 MAX
The 737 MAX is an evolution of earlier 737 generations, with more efficient engines, aerodynamic improvements such as its distinctive split-tip winglets, as well as airframe modifications. The 737 MAX series has four variants, offering seating capacities from 138 to 204 in typical two-class configurations, and ranges from 3,300 to 3,850nm (6,110 to 7,130km).
The 737 MAX 7, the MAX 8 (including the 200–seat MAX 200), and the MAX 9 replace the 737-700, 737-800, and 737-900 respectively. There is a further-stretched 737 MAX 10 currently under development.
As of June 2022, the 737 MAX (all variants) had 4,071 unfilled orders and 840 deliveries. If all of those orders and delivered, the 737 MAX will come second only to the 737-800 in terms of most 737 deliveries.
The 737 MAX is infamous for repeated failures of its Maneuvering Characteristics Augmentation System (MCAS), leading to two fatal crashes – Lion Air 610 (October 2018) and Ethiopian Airlines 302 (March 2019) – killing a total of 346 people, and quickly completely grounding all 737 MAX aircraft around the world. During 2019, 2020, and 2021 a very significant number of 737 MAX orders were canceled.
Subsequent investigations found Boeing was attempting to cover up defects and also noted failures in the FAA’s aircraft certification processes.
Boeing embarked on a significant program of modifications to existing MAX aircraft and design changes for new MAX aircraft, leading to a November 2020 FAA clearance for the 737 MAX to return to service, subject to pilot re-training.
Aviation authorities from other countries began to follow the FAA’s lead, with the Canadian and European authorities providing clearance in January 2021, and the Chinese authorities in December 2021. Most, but not all, countries have now lifted their 737 MAX bans.
737 MAX 7
This is the shortest 737 MAX with a typical 2-class capacity of 138 to 153 seats. The 737 MAX 7’s original delivery date of early January 2019 was delayed until late 2021.
Key MAX 7 customers include Southwest Airlines, Allegiant Air, and WestJet.
737 MAX 8
The MAX 8 is the first variant with delivery in 2017. The MAX 8 is also the most popular MAX variant to date.
At almost 4m longer than the MAX 7, the MAX 8 has a higher seating capacity of 162 to 178 seats in typical 2-class cabin configurations.
There is also a high seating density version of the MAX 8 named the MAX 200 with seating for up to 200 passengers in a single class seating configuration; this variant is popular with a number of ‘low cost’ airlines.
Key MAX 8 customers include Southwest Airlines, VietJet, SpiceJet, Ryanair, American Airlines, and flydubai.
737 MAX 9
The 737 MAX 9 is longer than the MAX 8 and can seat 178 to 193 passengers in typical 2-class cabin configurations.
The 737 MAX 9 started flying commercially in 2018 with Thai Lion Air. Other key customers include United Airlines, Alaska Airlines, and flydubai.
737 MAX 10
To help Boeing and the 737 MAX generation compete better with Airbus’ increasingly successful A321neo, the 737 MAX 10 was developed.
The MAX 10 is the longest 737 variant ever and has a potential 2-class seating capacity of 188 to 204, or up to 230 seats in a single cabin class configuration. This variant has received very sizeable orders from United Airlines, some of which are MAX 9 converted orders.
The first 737 MAX 10s are expected to be delivered in 2023, assuming timely conclusion of prolonged and delayed FAA certifications.
Other 737 Variants
The 737 is not just a commercial passenger aircraft, there are a number of non-passenger variants, including:
- 737-700C (cargo/passenger convertible) – This variant is based on the 737-700 fuselage and 737-800 wings. It has a forward cargo door. In the passenger layout, the 737-700C can carry up to 149 passengers. In the cargo configuration, it can carry up to 18.8 tonnes of cargo. The ceiling, sidewalls, and overhead bins remain in the interior when the 737-700C is configured for cargo.
- C40A – This is a US Navy airlift aircraft derived from the 737-700C, with flexible configurations including 120 passengers, or eight pallets of cargo, or a combination consisting of three cargo pallets and 70 passengers. The 737-700C has been modified to provide a large cargo door and strengthened wings and landing gear. The C40A provides long-range, high-priority logistical airlift support.
- 737 AEW&C (737-700W) – This is an airborne early warning and control (AWAC) aircraft, based on the 737-700 and operated by the Australian Government, the Turkish Air Force, the Republic of Korea Air Force, and the US Navy.
- P-8 Poseidon (737-800A) – Poseidon is a long-range maritime patrol and reconnaissance aircraft based on the 737-800. This aircraft was originally developed for the US Navy, but has also been sold to seven different countries around the world. The P-8 is based on an extended range version of the 737-800.
There are also business jets based on the 737 which date back to the 737-300 production days in the late 1980s. These aircraft were renamed the Boeing Business Jet (BBJ) as part of the 737NG phase of production. Three original BBJ variants were made available:
- The BBJ1 was the first to be launched in 1996, and the first delivery was in 1998. It is based on the 737-700, but with some features (including a stronger landing gear and increased range) of other 737NG variants.
- The BBJ2 was launched in 1999 and was first delivered in 2001. It is based on the 737-800 and offers an increased range, and 25% more cabin space than the BBJ1.
- The BBJ3 is a larger variant, based on the 737-900ER, so far orders have been few and far between.
More recently, Boeing launched the BBJ Max 7, BBJ MAX 8, and BBJ MAX 9.
Summary
The 737 is a constantly evolving Boeing aircraft that has been in production for more than five decades. The 737’s evolution has often occurred under competitive pressure from other manufacturers, notably Airbus and its A320 family.
Despite its popularity with airline customers, the 737 has not been without controversy.
The 737 MAX air crashes in 2018 and 2019 seriously dented customer confidence in the MAX program and in Boeing. Boeing is now starting to recover from this with the majority of aviation authorities having now cleared the 737 MAX to return to the skies.
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