Background When regular Boeing customer
United Airlines bought the more technologically advanced
Airbus A320 with
fly-by-wire controls, this prompted Boeing to update the slower, shorter-range
737 Classic variants into the more efficient, longer New Generation variants. In 1991, Boeing initiated development of an updated series of aircraft. After working with potential customers, the
737 Next Generation (NG) program was announced on November 17, 1993.
Testing . The first NG to roll out was a 737−700, on December 8, 1996. This aircraft, the 2,843rd 737 built, first flew on February 9, 1997, with pilots Mike Hewett and Ken Higgins. The prototype 737−800 rolled out on June 30, 1997, and first flew on July 31, 1997, piloted by Jim McRoberts and again by Hewett. The smallest of the new variants, the −600 series, is identical in size to the −500, launching in December 1997 with an initial flight occurring January 22, 1998; it was granted FAA certification on August 18, 1998.
Delta Air Lines received the first Next-Gen 737 model with this brake package, a 737-700, at the end of July 2008. The CFM56-7BE (Enhanced) nacelle began testing in August 2009 to be used on the new 737 PIP (Performance Improvement Package) due to enter service mid-2011. This new improvement is said to shave at least 1% off the overall drag and have some weight benefits. Overall, it is claimed to have a 2% improvement on fuel burn on longer stages. In 2015, Boeing offered a single wing-root mounted LED light package for all 737 NG airframes, replacing the old HID light sets which are located in different places across the fuselage.
Enhanced Short Runway Package This short-field design package is an option on the 737-600, -700, and -800 and is standard equipment for the new 737-900ER. These enhanced short runway versions could increase pay or fuel loads when operating on runways under . Landing payloads were increased by up to 8,000 lb on the 737-800 and 737-900ER and up to 4,000 lb on the 737-600 and 737-700. Takeoff payloads were increased by up to 2,000 lb on the 737-800 and 737-900ER and up to 400 lb on the 737-600 and 737-700. The package includes: • A winglet lift credit, achieved through additional winglet testing, that reduces the minimum landing-approach speeds. • Takeoff performance improvements such as the use of sealed
leading-edge slats on all takeoff flap positions, allowing the airplane to climb more rapidly on shorter runways. • A reduced idle thrust transition delay between approach and ground-idle speeds, which improves stopping distances and increases field-length-limited landing weight • Increased flight-spoiler deflection from 30 degrees to 60 degrees, improving
aerodynamic braking on landing. • A two-position tail skid at the rear of the aircraft to protect against inadvertent
tailstrikes during landing, which allows higher aircraft approach attitudes and lower landing speeds The first enhanced version, line number 1843, registered as PR-GTA, was delivered to
Gol Transportes Aéreos (GOL) on July 28, 2006. At that time, twelve customers had ordered the package for more than 250 airframes. Customers include: GOL,
Alaska Airlines,
Air Europa,
Air India,
Egyptair, GE Commercial Aviation Services (GECAS),
Hapagfly,
Japan Airlines,
Pegasus Airlines,
Ryanair,
Sky Airlines and
Turkish Airlines.
Performance Improvement Package (PIP) Stage II: Engine Enhancement Program The
CFM56-7BE (Enhanced) engines were introduced in mid-2015 as part of the PIP (Performance improvement package) for the 737 Next Generation aircraft. It provides: • 2% improvement in fuel consumption. • 2% reduction in carbon emission. • Retractable take-off light, which was located on the fuselage below the ram air intakes. The federal judge presiding the case sided with Boeing, and a subsequent court of appeal also ruled in favor of the company. A 2010 documentary by
Al Jazeera alleged that in three crashes involving 737NGs—
Turkish Airlines Flight 1951,
American Airlines Flight 331, and
AIRES Flight 8250—the fuselage broke up following impact with the ground because of the defective structural components that were the subject of the 2005 lawsuit. However, the accident investigations in all three cases did not highlight any link between post-impact structural failures and manufacturing issues. During an inspection of a 737NG in 2019 that had 35,000 flights,
fatigue cracks were found on a fuselage-to-wing attachment known as a "pickle fork", designed to last a lifetime of 90,000 flights. Boeing reported the issue to the
FAA at the end of September 2019, and more planes showed similar cracking after inspection. The cracks were found in an airliner with more than 33,500 flights, when it was stripped down for conversion to freighter. Aircraft with more than 30,000 flights (15 years at 2,000 flights per year) should be inspected within one week, while those with over 22,600 flights (11 years) should be inspected within one year. The FAA
Airworthiness Directive (AD) was issued on October 3, 2019. Of the 500 first inspected aircraft, 5% () had cracks and were grounded; Boeing expected to repair the first aircraft three weeks after the issuance of the directive, serving as the template for the resulting
Service bulletin. Of the 810 examined aircraft over 30,000 cycles, 38 had structural cracks (%), leaving 1,911 737NGs over 22,600 cycles to be inspected within their next 1,000 cycles, i.e., nearly all of the US in-service fleet of 1,930. By early November, 1,200 aircraft were inspected, with cracks on about 60 (5%). Cracks were discovered near fasteners outside the original area in four airplanes. On November 5, Boeing recommended expanding the checks to include them, to be mandated in a November 13 FAA . Aircraft below 30,000 cycles were to be reinspected within 1,000 cycles, within 60 days above. About one-quarter of the global NG fleet of 6,300 aircraft were to be inspected. Following the
contained engine failure of the
Southwest Airlines Flight 1380 on April 17, 2018, the
National Transportation Safety Board (NTSB) recommended on November 19, 2019, to redesign and retrofit its
nacelle for the 6,800 airplanes in service.
Production went from 31.5 (2010) to 52 (2018) per month Boeing was to increase 737 production from 31.5 units per month in September 2010 to 35 in January 2012 and to 38 units per month in 2013. Production rate was 42 units per month in 2014, and was planned to reach rates of 47 units per month in 2017 and 52 units per month in 2018. In 2016, the monthly production rate was targeted to reach 57 units per month in 2019, even to the factory limit of 63 units later. A single airplane was then produced in the
Boeing Renton Factory in 10 days, less than half what it was a few years before. The empty
fuselage from
Spirit AeroSystems in
Wichita, Kansas, enters the plant on Day 1.
Electrical wiring is installed on Day 2 and
hydraulic machinery on Day 3. On Day 4 the fuselage is crane-lifted and rotated 90 degrees,
wings are mated to the airplane in a six-hour process, along with
landing gear, and the airplane is again rotated 90 degrees. The final assembly process begins on Day 6 with the installation of
airline seats,
galleys,
lavatories,
overhead bins, etc. Engines are attached on Day 8 and it rolls out of the factory for
test flights on Day 10. Boeing stopped assembling passenger 737NGs in 2019. The last aircraft assembled was a 737-800 registered PH-BCL delivered to KLM in December 2019; the last two deliveries were to China Eastern Airlines on January 5, 2020. Production of the P-8 Poseidon variant continues. The FAA has proposed a fine of approximately $3.9 million for Boeing's alleged installation of the same faulty components of the
737 MAX on some 133 737 NGs.
Further developments first flew on January 29, 2016. From 2006, Boeing discussed replacing the 737 with a "clean sheet" design (internally named "
Boeing Y1") that could follow the
Boeing 787 Dreamliner. A decision on this replacement was postponed, and delayed into 2011. In 2011, Boeing launched the 737 MAX, an updated and
re-engined version of the 737NG with more efficient
CFM International LEAP-1B engines, and aerodynamic changes with distinctive split-tip
winglets. The first 737 MAX performed its first flight in January 2016. The fourth generation 737 MAX supersedes the third generation 737NG. Split Scimitar winglets became available in 2014 for the 737-800, 737-900ER, BBJ2 and BBJ3, and in 2015 for the 737-700, 737-900 and BBJ1. These resemble the 737 MAX's split winglet, though they are not identical. Split Scimitar winglets were developed by
Aviation Partners, the same Seattle-based corporation that developed the blended winglets; the Split Scimitar winglets produce up to a 5.5% fuel savings per aircraft compared to 3.3% savings for the blended winglets. Southwest Airlines flew their first flight of a 737-800 with Split Scimitar winglets on April 14, 2014. == Design ==