The Boeing 737 is an aircraft that will forever leave a mark on aviation as we know it. Developed into four main series, the original -100 and -200 variants, the classic -300/-400/-500 series, then the next generation -600/-700/-800/-900 series, and lastly and most recent, the 737 MAX, which is comprised of the MAX 7, MAX 8, MAX 9, and lastly the MAX 10.
The 737 is currently nearing the 10,000th airframe delivered. The 737 has been produced since 1966 at Boeing’s Renton plant outside Seattle, Washington. This jet is so vital to commercial aviation that at any given moment there are around 1,250 Boeing 737s in the sky. The 737 fulfills roles left open by aging narrow-body families.
Boeing 737 | Design
In the early 1960s, Boeing was looking into a way to produce an aircraft capable of flying low demand shorter routes. Currently, they had the single isle 707 which could fly transcontinental and could hop the Atlantic. They also developed the 727, based on the 707 this aircraft had less range and less passenger capacity, however, this made it perfect for short-range and low to medium demand routes. Boeing saw a hole, they had no aircraft capable of making short and skinny routes, and a dual jet on the 707’s airframe was a perfect choice. This aircraft would later be designated the ‘Boeing 737’ and would become one of the most iconic aircraft of commercial aviation.
The initial design was a slightly different 727, simply missing the middle S duct engine and in a 2-3 five abreast configuration. However, the famous Joe Sutter chose to move the engines under the wing. This would eliminate the need for additional support structures to hold up the heavy engines on the tail, thus allowing the 737 to have six abreast seating in the popular 3-3 configuration. Little did they know the design that was presented in 1964 by the chief project engineer would be one of the best ones that came off the production line. Soon the go-ahead by Boeing was given on the first of February in 1965; the legend was conceived.
Boeing 737 | Original Series
Orders/ Deliveries: 30/30
*Includes the -200C and T-43A
Note: As of October 31st, 2017
Just over two weeks after the go-ahead, the first order for 21 aircraft came from Lufthansa, making it the main commercial operator for the -100. A few months later in April, United Airlines placed an order, but not for the -100. United needed just a few more seats than the -100 could hold, so Boeing decided they could stretch the airframe just under six and a half feet to allow for more seats, this made the original design the -100, and the extended body design became the -200.
Boeing continued designing, however with two airframes at the same time instead of just one. They could not stall getting this aircraft produced, for they had many rivals such as Douglas’ DC-9, The BAC 1-Eleven, and the Fokker F28 have already been certified and in production. To speed up the 737’s design, it shared over 50% commonality with the slightly larger 727.
Because the engines were moved from the tail to under the wing strenuous wind tunnel testing had to occur to ensure it was meeting efficient standards, however, they also had to keep the aircraft riding low to the ground and make it easy to maintain. It was discovered that a small engine pylon to mount the JT8D directly below the wing would be the most efficient.
The fuselage construction was subcontracted out to Spirit AeroSystems instead of being built Boeing, the fuselages are still built by Spirit in their Wichita Kansas plant and are shipped to final assembly on rail. Final assembly was completed at Boeing Field, this was later moved to Renton however at the time Renton was maxed out with 707 and 727 production.
The -100 was tested by six different prototypes and in December of 1967, The FAA certified the -100 for commercial use. On the 28th of December Lufthansa took delivery of their first -100. Only 30 737-100s were ever produced, 21 going to Lufthansa. Few other commercial airlines purchased the -100, the rest went to the military and other customers.
The -200s maiden flight was a few months earlier in August of 1967. This aircraft was certified just about a week after the -100 in December. In April United’s first flight between Chicago and Grand Rapids cemented the -200s existence into commercial aviation. The higher seating capacity of the -200 was preferred over the -100.
Sales of the bird were very low the rest of the decade, Boeing was very close to cutting the cord of the aircraft but in 1972 the United States Air Force ordered the T-43, a slightly modified -200 variant. Many airlines in Africa used the cheap but effective aircraft which also kept the airframe alive. Boeing was limited on financial abilities in the early 70s. However, after limiting production of the 747 and canceling the Supersonic Transport enough funds were opened up to keep the program running.
The -200 was soon offered with a gravel kit. This option allowed the 737 to land on short, undeveloped, and quite poor runways. Alaska Airlines used the -200 gravel kit until 2007 because of its ability to land on undeveloped runways in the heart of Alaska. The gravel kit is still used by many Canadian airlines due to the number of rural undeveloped runways in Northern Canada that later 737s could not land on.
In 1988, after well over 1,000 737 aircraft delivered, the last Original 737 was delivered to Xiamen Airlines in August of that year. Deregulation for the United States airlines opened up the market for a six abreast aircraft for many airlines, this led to the development of the 737 Classic.
In 2008, the last Original 737s owned by an American airline was retired. However the -200 is still commonly used for commercial operations in Canada, Africa, and other undeveloped areas with lots of gravel, undeveloped runways.
Boeing 737 | Classic Series
Orders/ Deliveries: 1113/1113
Orders/ Deliveries: 486/486
Orders/ Deliveries: 389/389
Note: As of October 31st, 2017
Following airline deregulation, the need for an efficient single-aisle plane in the US grew. Now very low demand routes were more logical to be served. After the success of the previous 737s Boeing noticed the need for a further developed and more advanced aircraft. Initial development began in 1979, and early specifications were released at the Farnborough Airshow in 1980. Boeing selected the CFM-56 turbofan to power the classic series. Compared to the JT8D on the original 737s, this turbofan offered extremely large gains in efficiency and range.
Have you wondered why the 737s engines are egg-shaped? Due to the low ground clearance with the significantly larger engines, special modifications had to be done to maximize that clearance. The turbofan was placed in front of the wing instead of under the wing. This means the engine does not have to be mounted any further down, it’s top surface is almost even with the wing surface. To give further ground clearance the fan disc at the front was made slightly smaller, this sadly reduced the efficiency of the aircraft. To further increase the clearance, engine accessories, which are normally mounted below the engine, were moved to the bottom sides shaping the air intake oddly, giving the engine that squared off bottom look.
In 1981 both USAir (Later known as US Airways) and Southwest Airlines placed orders on the 737-300. The -300 first flew in early 1984 and was certified in November of that year. USAir received their first classic, then it was shortly thereafter delivered to Southwest. Winglet retrofits are available for the aircraft, winglet-equipped -300s are called the 737-300 Special Performance.
Piedmont ordered a stretched -300, to be later designated the -400. This aircraft first flew in February 1988 and entered service later that year. Stretched about ten feet, this aircraft was built to bridge the gap between the -300 and the 757-200, it heavily competed with the brand new Airbus A320 and McDonnell-Douglas MD-80 series. The -400 was the largest Classic series 737.
Lastly in 1987 Southwest airlines launched the -500 with an order for 30 aircraft. This aircraft was dubbed the -200 replacement because of similar passenger capacities and long range. It first flew in 1989 and entered service with Southwest Airlines in 1990.
The last classic was delivered to Air New Zealand in late 1999. Sadly the classics are being retired after almost two thousand built. A handful of 737-300s will be going through freighter conversion and be sold off to other companies. However, the demand for -400 and -500 freighters are very low. The military still has very strong uses for these aircraft, over fifteen different countries use the classics for various uses.
Boeing 737 | Next Generation Series
Orders/ Deliveries: 69/69
Orders/ Deliveries*: 1283/1279
Includes the -700C, -700W, and BBJ1
Orders/ Deliveries: 5174/4695 Includes the -800A, and BBJ2
Orders/ Deliveries: 570/499 *Includes the -900ER
Note: As of October 31st, 2017
After the release of the advanced Airbus A320 and the fact it was stealing previous Boeing-loyal airlines like Lufthansa, United, and American, Boeing gave the go-ahead on a replacement for their ageing 737 Classic series. The Next Generation improvement was abbreviated NG. Many major changes were performed on the new bird, however, it still shares commonality with the older 737s. Boeing chose to increase the wingspan over 16 feet, add newer and cleaner CFM-56, newer and more advanced cockpit and avionics system, and increasing the fuel capacity to allow transcontinental flights.
Built to compete with the Airbus A318, Boeing launched the 737-600. With a similar shape and dimensions of the -500, Boeing’s 737-600 was produced. It did not have the winglets as a standard option, unlike the rest of the NG family. Only two main airlines purchased the -600, WestJet and Scandinavian (SAS) The first was delivered in 1998 and the last in 2006. The -600 clearly did not sell like hotcakes and only 69 were ever ordered and delivered.
In late 1996 the very first NG was rolled out of Renton, the 737-700 was based heavily on the -300.This aircraft first flew in February of 1997. The -700 was built to heavily compete with the A319. Four -700s were used for certification. The 737-700 seats between 137 or 149 passengers depending on the class configuration. Boeing later developed the -700C, the seats, and interior can be removed to add cargo. The United States Navy purchased the first -700Cs designated the C-40 ‘Clipper’. ANA placed an order for another -700 variant, the -700ER to compete with the A319LR. This combines the 700s airframe with the 800s wings and landing gear. Seating ten fewer passengers than the standard -700 its range is, however, greatly increased.
Rolled out in June 1997, and flying a month later in July 1997, the 737-800 was built as a replacement for the 737-400, various MD-80 series aircraft, and some 727s, and to compete with the A320. Only three -800s were used for program certification. The -800 seats between 162 and 189 people depending on the class configuration. It was launched with an order in 1994 and first delivered in 1998.
After the first three NGs were introduced, Alaska Airlines wanted a longer bird. Boeing announced the -900 series with a firm order from Alaska in 1997 and the first deliveries commenced in 2001. The fuel capacity was the same as the -800 which means the range was heavily dampened. The big issue was the -900 featured the same exit configuration as the -800 limiting the seating capacity to just 189 in a single class configuration. This also limited the competition with the Airbus A321. Boeing later introduced the 737-900ER, this added an additional exit door in the back too allow for more seats, up to 220 in a single class configuration. This makes the -900 compete even more with the Airbus A321.
Many Next Generations are still yet to be delivered and while it isn’t Boeing’s most advanced 737 series, it is still very advanced, efficient, and will be sold as a cheaper alternative for the 737 MAX.
Boeing 737 | MAX Series
ICAO: Not determined, most likely will be B3XM
Orders/ Deliveries (all variants): 3954/34
Note: As of October 31st, 2017
Instead of the CFM-56 used on the previous variants of the 737, the brand new MAX will use the CFM-Leap engine, this high-bypass engine is one of the most efficient capable for using on single aisle aircraft. In 2011 Boeing gave the go-ahead on the MAX, promising over 15% less fuel burn than the Airbus A320, and just less than 5% less fuel burn than the new Airbus A320 NEO. Later improvements like the split scimitar winglet will further increase the efficiency of the aircraft.
Announced at the Farnborough Airshow in 2016 and based off of the NG Boeing 737-700, seating up to twelve more passengers than the -700 the MAX-7 was introduced. The production of the very first aircraft began in October of 2017, this aircraft is projected to be delivered in January 2019 with Southwest Airlines and later that year with multiple other carriers. The MAX-7 will compete with the A319 NEO.
The first MAX variant announced was the MAX-8. A redesigned 737-800 and be a step up in size from the MAX-7. The MAX-8 was the first MAX to be in commercial service, the first flight being OD803 between Kuala Lumpur and Singapore. This aircraft heavily competes with the Airbus A320. Ryanair asked for a MAX-8 with an even higher seating capacity, dubbed the 737 MAX-200 this aircraft is the MAX-8 but with an extra pair of exits behind the wing, allowing up to 200 aircraft and 5% more cost-effective than the standard MAX-8, this is projected to enter service in 2019. This aircraft heavily competes with the Airbus A320 and A321.
The 737 MAX-9 will be a replacement for the 737-900. It was rolled out in March 2017 and took off one month later in April. It is projected to enter service in the first few months of 2018. Only two MAX-9s are being used for the program testing, this will slow down the testing process slightly. This was built to compete with the A321, however, it did not perform very effective against the Airbus.
The 737 MAX-9 was outsold five to one compared to the Airbus counterpart, the A321 NEO. Boeing proposed the MAX-10, this would have a much higher seating capacity and would be based on the -900ER. Requiring improvements like telescoping landing gear and a slightly upgraded LEAP-1B engine. In just a few months the MAX-10 has racked up 240 orders from over 10 customers, however many companies, like United, transferred over previous orders for other MAX aircraft for the MAX-10.
Boeing 737 | Boeing Business Jets (BBJ)
Since the NG was released, Boeing has offered a lineup of BBJ aircraft. Based off of the 737-700ER the BBJ1 is the smallest currently in the lineup. Based off of a slightly modified 737-800 the BBJ2 is the medium-size alternative. Lastly, based on of the -900ER is the BBJ3, this is the largest of the Next Generation BBJs, however, only three have been sold.
With the 737 MAX, Boeing proposed the BBJ MAX 8 and MAX 9, in October the BBJ MAX 7 was rolled out featuring 10% less operating costs than the BBJ1 and being bigger, further increasing the BBJ family.
Boeing 737 | Winglets
The winglet was not developed when the first 737s came out, however, companies have received certification for retrofit capabilities on the older aircraft. Quiet Wing Corp received certification on their retrofit kit for the -200 and -200A.
Aviation Partners designed and built the blended winglet standard on the 737 NG series (except the -600) and was available for retrofit. This winglet accounted for over 3% fuel savings on both the standard and retrofit. Southwest Airlines saw the potential for these fuel savings and retrofitted all of their -300 and -500 classic series aircraft with the new winglet. This saved them thousands if not millions of dollars every year until they were retired.
Aviation Partners also designed the Split Scimitar winglets, in 2014 it was approved for use on the -800, -900ER, BBJ2, and the BBJ3. Later in 2015, it was approved for use on the -700, -900, and the BBJ1, these advanced winglets save over 5% fuel compared to an NG without winglets.
The 737 MAX will also feature a split scimitar winglet, however, it will be designed by Boeing and not subcontracted out, nicknamed the Advanced Technology (AT) winglet, this winglet looks like a more blocky Split Scimitar, however, it is supposed to be even more efficient than the Split.
Boeing 737 | Interior
The 737 has never had a 737 specific interior, the classic interior was based on the 757, it featured plain paneling and limited space overhead containers. For the Next Generation interior, designs from the new 777 were used. It features curvier panels and larger overhead bins. After the release of the 787, even though no new 737 variants was developed, in 2010 Boeing introduced the Sky Interior, this interior introduced pivoting overhead bins, maximizing overhead storage space, LED mood lighting was also introduced with the new interior. The Sky Interior will also come standard on all 737 MAX aircraft.
Boeing 737 | Importance in Aviation
Boeing’s 737 is one of the most important aircraft in aviation history. While it’s shape isn’t iconic like the Concorde or 747, its history, and how common the aircraft is in the aviation world make it iconic.
Without the 737 we would not see the same amount of air travel we see today, competition from Airbus would likely not be seen, and because it doesn’t exist the importance and emphasis on regional aviation would not be as strong. Because the 737 pioneered regional jet travel, without it we would still likely see more props on these routes. Or older inefficient aircraft.
Boeing 737 | Works Cited
Special thanks to @awoodbay for proofreading and making changes, thanks!
Excuse the summary, I don’t want them having the auto-resize clogging up the back half of the article.
Click to Show
Which Aircraft Should I Do Next?
- Boeing 747