Friday, March 27, 2015

Flashback Friday: The Boeing 737 NG Family

By Luis Linares / Published March 27, 2015

737 NG Rollout

The Boeing 737-700 was the first NG to rollout of Boeing’s Renton pant:  Photo courtesy of Boeing

The Boeing 737 family of airplanes has been flying passengers around the world since 1968.  In addition, Boeing has delivered almost 8,500 of these airplanes from over 12,700 orders.  These numbers encompass four generations of the 737, including the future MAX variants.  The most successful of the first three generations of is the “Next Generation” (NG), which entered service in 1997, with more than 5,300 deliveries, and almost 1,600 on order, with a current production rate of over 42 airframes per month.  On this Flashback Friday, we look back at the history of the iconic 737 NG.

Development and Testing

In the mid-1980s the first major upgrade of the Boeing 737 family began to enter service.  This series, known today as the “Classic” consists of the 737-300, -400, and -500.  The most visible differences between the “Classic” and original -100/-200 models were newer, more efficient engines, a different tail design, extended wings, and cockpits fitted with the Electronic Flight Instrumentation System (EFIS), which was a new technology at the time.

Two members of the “Classic” generation – Boliviana de Aviación Boeing 737-300 (L) and Vision Airlines (operating for Miami-based charter Havana Air) Boeing 737-400 (R):  Photos by Luis Linares / AirwaysNews

The 737 family had been challenged by significant competition since the first aircraft entered service on February 10, 1968.  However, on April 18, 1988, European manufacturer Airbus introduced the A320 into service, marking the beginning of a historic rivalry in the narrowbody market that continues to this day.  The A320, which incorporated the latest technologies of the time, forced Boeing to reevaluate the 737.

EXTRA:  Inside Boeing’s 737 Renton Factory as They Take It to the “MAX”: Part One

EXTRA:  Inside Boeing’s 737 Renton Factory as They Take It to the “MAX”: Part Two

Boeing consulted with potential customers on the future of the 737, and this led to the launch of the NG program on November 17, 1993.  The NGs would come in four different lengths with the series designators (from shortest to longest) -600, -700, -800, and -900.  The basic fuselage shape of the original 737 would incorporate the most significant upgrades of the family, such as a new and larger wing, as well as new quieter and more efficient engines.

EXTRA:  Boeing 737 NG Memorabilia and Marketing

737 NG Brochure

Brochure from 2002 depicting the 737 NG family: Image courtesy of AirwaysNews

The new improvements would make NG a brand new aircraft in terms of performance, especially greater range that would allow transcontinental flights in the U.S. and Canada.  The new wing allowed for a greater typical cruising speed from the Mach 0.74 on the “Classic” to a faster Mach 0.78.  Furthermore, on the inside, the NG adopted some of the features of the Boeing 777, which entered service in 1995.  For example, the passenger cabin would have larger storage bins and curved ceiling panels.  Finally, a new glass cockpit incorporated the modern primary flight and navigation displays of the 777, but could be reprogrammed to display the EFIS gauges common in the “Classic,” allowing crews in airlines with “Classics” and NGs to operate both aircraft.

The first NG rolled out on December 8, 1996.  The prototype was a -700 series, essentially a replacement of the -300, first flew on February 9, 1997.  The -800, intended to replace the -400, rolled out on June 30, 1997 and first flew a month later on July 31.  The “flying football,” the -600, which would replace the -500, rolled out on December 8, 1997, and had its maiden flight on January 22, 1998.

In 1997, as the initial variants rolled out, Boeing launched the -900, the longest model of the 737 family.  The first -900 rolled out on July 23, 2000, and flew for the first time over a week later on August 3.  Boeing also planned for private and military variants of the NG.

The Boeing 737 NG Family



WestJet Airlines Boeing 737-600: Photo by Luis Linares / AirwaysNews

The -600 entered service with Scandinavian Airlines on October 25, 1998.  The -600 can seat 108 passengers in a typical two-class layout (the same as a -500) and can travel up to 3,050 nmi (3,509 mi or 5,648 km), 21% more than the -500.  Its CFM 56-7B20 engines provide 22,700 lbf (101 kN) of thrust each.

Boeing only produced and delivered 69 -600s, with the last delivery taking place in 2006.  Economics contributed to the short production life of the “flying football.”  Customers could fly the larger -700 with more passengers and cargo for essentially the same cost, while generating additional revenue.


Southwest Airlines was the first airline to fly the -700, on January 18, 1998.  In a standard two-class arrangement, the -700 can seat 128 passengers, like the -300 it replaced.  The -700 has a range of 3,365 nmi (3,871 mi or 6,230 km), a 32% increase compared to the -300.  The CFM 56-7B26 powers the -700, and each of these engines provide up to 26,300 lbf (117 kN) of thrust.

Southwest Airlines is the launch customer and biggest operator of the Boeing 737-700:  Photos by Luis Linares / AirwaysNews

Launch customer Southwest Airlines has the largest fleet of -700s with 441, plus 20 on order and 37 options.  Boeing also designed a -700C (convertible) version that can quickly be configured to all-passenger or all-cargo with the help of a side cargo door on the left side.  Furthermore, the C-40 is the designation for the VIP and military transport variant used by the U.S. Air Force and Navy, and other air forces around the world fly the 737 AEW&C (Airborne Early Warning and Control).  To date, Boeing has delivered more than 1,050 commercial passenger -700s.


The -700 entered a niche market in the form of the -700ER on February 16, 2007.  All Nippon Airways launched this variant with the intent of transporting customers much farther than the -700, either in a 38-seat all-business class setting or a 24 business/20 premium economy layout.  The design is based on the business variant (BBJ – Boeing Business Jet) of the -700, and the airplane can fly up to 5,510 nmi (6,334 mi or 10,200 km), thanks to an additional fuel tank.


The -800 is by far the most successful member of not just the NG, but of the entire 737 family, with more than 6,000 orders – more than 4,800 of those orders currently in service.  German airline Hapag-Lloyd (today part of the TUI group) introduced the -800 into service on April 24, 1998.  Furthermore, from the late 1990s to early 200s, the -800 became a popular replacement for the 727-200, especially for U.S. operators Alaska Airlines, American Airlines, ATA Airlines, Continental Airlines, and Delta Air Lines.


Out of all the Boeing 737 variants, since introduction in 1968, the -800 has been the best seller” with over 6,000 orders:  Photos by Luis Linares / Airways News

The -800 is much more than a replacement for the “Classic” -400.  For instance, it is 10 ft (3 m) longer and carries 160 passengers in a standard two-class arrangement, 14 more than the -400.  In addition, its maximum range of 3,060 nmi (3,520 mi or 5,665 km) is 25% better than that of the -400.  Furthermore, with airlines focusing more on bottom lines, the -800 has become far more preferable than the -700 since it can fly more people and cargo for roughly the same cost of a -700, but with higher revenue.

Irish ultra-low-cost carrier Ryanair has the largest -800 fleet, with more than 300 examples in service and over 170 unfulfilled orders.  Boeing also derived the U.S. Navy’s P-8 “Poseidon” from the -800.  Moreover, the company made a business jet version, designated the BBJ-2.


The -900 is the longest of the NG family, and launch customer Alaska Airlines entered it into service on May 27, 2001.  The -900 can carry 17 more passengers than the -800 is a typical two-class configuration, but this means a lower range than the -800.  This range penalty and other limitations contributed to only 52 -900s being delivered.


Boeing did not sit back and let the -900 go down as a failure.  Instead, it launched the -900ER on July 18, 2005, and this would be a vast improvement over the -900.  Indonesian airline Lion Air became the launch customer and began service with the -900ER on May 1, 2007.


Delta Airlines Boeing 737-900ER:  Photo by Luis Linares / AirwaysNews

Boeing added an additional exit row between the over-wing exits and the rear entry door on each side of the fuselage.  The manufacturer also installed a flat rear pressure bulkhead.  This resulted in a seating capacity of 180 passengers in a typical two-class setting.

Two CFM 56-7B27 engines power the -800 and -900 variants of the 737 NG, and each provides 27,300 lbf (121.4 kN) of maximum thrust.  With two auxiliary fuel tanks, the -900ER can fly 3,200 nmi (3,681 mi or 5,925 km).  There are over 500 -900ERs in service with more than 200 on order.  The business variant of the -900ER is the BBJ-3.

EXTRA:  PHOTO SLIDESHOW: AirwaysNews Explores Boeing’s Renton Plant

Continuous Improvement


Gol Airlines Boeing 737-800: Photo by Luis Linares / AirwaysNews

Boeing has been very proactive in looking for ways to make the NG even better.  For example, loyal Boeing customer Gol Airlines approached the manufacturer about improving the performance of the NG at Brazilian airports with short runways, notably Rio de Janeiro’s Santos Dumont Airport, where the two parallel runways measure 4,341 ft (1,323 m) and 4,200 ft (1,260 m).  In 2006, Boeing began to deliver Gol Short Field Performance Package (SFP)-equipped 737-800s with upgrades such as sealed leading edge slats that allowed the aircraft to take-off from the smaller airports and increased flight spoiler deflection for better landing performance.  Boeing offers the SFP as an optional upgrade for existing NGs, and the company made it standard on all -900ERs.

With improved navigation technology and Traffic Collision Avoidance Systems (TCAS), Boeing began to roll out later NGs without the “eyebrow” windows on top of the cockpit.  This also helped prevent fatigue in that part of the fuselage.  Basically, by having a more continuous shape without the two cut out window sections, there is less susceptibility to cracking over time.

In July 2008, Boeing changed the brakes on the NG.  By introducing new carbon brakes in place of steel ones, Boeing saved airlines 500 to 700 lb (250 to 320 kg) of weight, or up to 0.5% reduction in fuel burn.  Moreover, in 2010, the manufacturer introduced the “Boeing Sky Interior” on all new NGs, and it features a smaller version of the curved, pivoting overhead bins originally introduced on the 777 in 1994.  This interior enhancement also includes new sidewalls that make windows appear to be bigger and LED mood lighting.

The 737 NG received ETOPS-180 certification, a 60-minute bump from its original ETOPS-120, in 1999.  This allowed NGs to be three hours from a suitable airfield, in case of emergency scenarios like engine failure or cabin decompression.  This enabled U.S. carriers to fly their NGs from the West Coast to Hawaii.  Boeing also began to offer a Head Up Guidance System (HGS) on the right seat of the cockpit to give the captain full situational awareness in one screen, especially during take-off and landing.

Another important improvement on the NG was the introduction of blended winglets manufactured by Aviation Partners Boeing (APB) on passenger NGs, except the -600, in 2000.  These were already standard on the BBJs.  The winglets provide aerodynamic improvements, such as better climb performance, and also deliver fuel savings and a range increase of 75 nmi (87 mi or 140 km) on the -700 and 55 nmi (62 mi or 100 km) on the -800.  Blended winglets come standard on all NGs and are a retrofit upgrade for NGs built before their introduction.

The visual difference between APB blended winglets (L) and split scimitar winglets (R):  Photos by Luis Linares / AirwaysNews

The next major upgrade for the 737 family is the MAX, which will enter service in 2017.  Among its key features are new CFM LEAP-1B engines and APB split scimitar winglets.  These enhancements will result in a 10 to 12% improvement in fuel burn over the NG.  The MAX will compete with the Airbus A320 neo (new engine option) family, and its design also provided the NG with an additional improvement since APB now offers split scimitar winglets for the -800 and -900ER.  Blended winglets offer the NG a 3.5% fuel savings, while split scimitar ones offer an improvement of up to 5.5%.


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