Editing Boeing 737 (section)

== Development ==
=== Initial design ===
[[File:1964 Boeing 737 concept.png|thumb|1964 concept with tail mounted engines]]

Boeing had been studying short-haul jet aircraft designs, and saw a need for a new aircraft to supplement the [[Boeing 727|727]] on short and thin routes.<ref name="nyt transport news">"[https://www.nytimes.com/1964/07/17/transport-news-boeing-plans-jet.html Transport News: Boeing Plans Jet.] {{Webarchive|url=https://web.archive.org/web/20170821213438/http://www.nytimes.com/1964/07/17/transport-news-boeing-plans-jet.html |date=August 21, 2017}}" ''[[The New York Times]]'', July 17, 1964. Retrieved: February 26, 2008.</ref> Preliminary design work began on May 11, 1964,{{sfn|Endres|2001|p=122|ps=}} based on research that indicated a market for a fifty to sixty passenger airliner flying routes of {{Convert|50|to|1000|mi|-2}}.<ref name="nyt transport news" />{{sfn|Sharpe|Shaw|2001|p=12|ps=}}

The initial concept featured [[podded engine]]s on the aft fuselage, a [[T-tail]] as with the 727, and five-abreast seating. Engineer [[Joe Sutter]] relocated the engines to the wings which lightened the structure and simplified the accommodation of six-abreast seating in the fuselage.<ref name=FG170406 /> The engine [[nacelle]]s were mounted directly to the underside of the wings, without pylons, allowing the [[landing gear]] to be shortened, thus lowering the fuselage to improve baggage and passenger access.{{sfn|Sutter|2006|pp=76–78}} Relocating the engines from the aft fuselage also allowed the [[horizontal stabilizer]] to be attached to the aft fuselage instead of as a T-tail.{{sfn|Sharpe |Shaw|2001|p=17|ps=}} Many designs for the engine attachment strut were tested in the wind tunnel and the optimal shape for high speed was found to be one which was relatively thick, filling the narrow channels formed between the wing and the top of the nacelle, particularly on the outboard side.[[File:Boeing 737 patent USD206035S.jpg|thumb|October 18, 1966, Jet aircraft patent, filed June 22, 1965, by John Steiner and [[Joe Sutter]] for Boeing]]

At the time, Boeing was far behind its competitors; the [[Sud Aviation Caravelle|SE 210 Caravelle]] had been in service since 1955, and the [[BAC One-Eleven]] (BAC-111), [[McDonnell Douglas DC-9|Douglas DC-9]], and [[Fokker F28]] were already into flight certification.<ref name="german order" /> To expedite development, Boeing used 60% of the structure and systems of the existing 727, particularly the fuselage, which differs in length only. This 148-inch (3.76 m) wide fuselage cross-section permitted six-abreast seating compared to the rivals' five-abreast. The 727's fuselage was derived from the 707.{{sfn|Sharpe|Shaw|2001|p=13|ps=}}

The proposed wing [[airfoil]] sections were based on those of the 707 and 727, but somewhat thicker; altering these sections near the nacelles achieved a substantial drag reduction at high Mach numbers.<ref>Olason, M.L. and Norton, D.A. "Aerodynamic Philosophy of the Boeing 737", AIAA paper 65-739, presented at the AIAA/RAeS/JSASS Aircraft Design and Technology Meeting, Los Angeles California, November 1965. Reprinted in the AIAA Journal of Aircraft, Vol. 3 No. 6, November/December 1966, pp. 524–528.</ref> The engine chosen was the [[Pratt & Whitney JT8D]]-1 low-bypass ratio turbofan engine, delivering {{Convert|14500|lbf|kN|lk=on}} of thrust.{{sfn|Shaw|1999|p=6|ps=}}

The concept design was presented in October 1964 at the [[Air Transport Association]] maintenance and engineering conference by chief project engineer Jack Steiner, where its elaborate [[high-lift device]]s raised concerns about [[aircraft maintenance|maintenance]] costs and dispatch reliability.<ref name=FG170406>{{cite news |url= https://www.flightglobal.com/news/articles/analysis-half-century-milestone-marks-737s-endurin-435787/ |title= Half-century milestone marks 737's enduring appeal |date= April 7, 2017 |author= Stephen Trimble |work= FlightGlobal}}</ref>

=== Major design developments ===
[[File:Boeing 737 family v1.0.png|thumb|upright=1.8|A comparison of the first three generations]]

The original 737 continued to be developed into thirteen passenger, cargo, corporate and military variants. These were later divided into what has become known as the four generations of the Boeing 737 family:
* The first generation "Original" series: the 737-100 and -200, also the military T-43 and CT-43, launched February 1965.
* The second generation "Classic" series: 737-300, -400 and -500, launched in 1979.
* The third generation "Next Generation" series: 737-600, -700, -800 and -900, also the military C-40 and P-8, launched late 1993.
* The fourth generation 737 MAX series: 737-7, -8, -9 and -10, launched August 2011.

=== Launch ===
The launch decision for the $150 million (~${{Format price|{{Inflation|index=US-GDP|value=150000000|start_year=1965}}}} in {{Inflation/year|US-GDP}}) development was made by the board on February 1, 1965.{{sfn|Sharpe|Shaw|2001|p=13|ps=}} The sales pitch was big-jet comfort on short-haul routes.<ref name="ar 2017-04-23">{{cite web |last1=Thomas |first1=Geoffrey |title=Boeing's 737: The plane that almost never was. |url=https://www.airlineratings.com/news/boeings-737-the-plane-that-almost-never-was/ |website=Airline Ratings |access-date=June 3, 2023 |language=en-AU |date=April 23, 2017}}</ref>

[[Lufthansa]] became the launch customer on February 19, 1965,{{sfn|Sharpe|Shaw|2001|p=13|ps=}} with an order for 21 aircraft, worth $67&nbsp;million (~${{Format price|{{Inflation|index=US-GDP|value=67000000|start_year=1965}}}} in {{Inflation/year|US-GDP}})<ref name="german order">"German Airline Buys 21 Boeing Short-Range Jets." ''[[The Washington Post]]'', February 20, 1965. Retrieved: February 26, 2008.</ref> after the airline had been assured by Boeing that the 737 project would not be canceled.<ref name="Wallace">Wallace, J. [http://www.seattlepi.com/default/article/Boeing-delivers-its-5-000th-737-1195654.php "Boeing delivers its 5,000th 737."] {{Webarchive|url=https://web.archive.org/web/20120309074239/http://www.seattlepi.com/default/article/Boeing-delivers-its-5-000th-737-1195654.php |date=March 9, 2012}} ''Seattle Post-Intelligencer'', February 13, 2006. Retrieved June 7, 2011.</ref> Consultation with Lufthansa over the previous winter had resulted in the seating capacity being increased to 100.{{sfn|Sharpe|Shaw|2001|p=13|ps=}}

On April 5, 1965, Boeing announced an order by [[United Airlines]] for 40 737s. United wanted a slightly larger capacity than the 737-100, so the fuselage was stretched {{Convert|91|cm|order=flip}} ahead of, and {{Convert|102|cm|order=flip}} behind the wing.{{sfn|Sharpe|Shaw|2001|p=17|ps=}} The longer version was designated the 737-200, with the original short-body aircraft becoming the 737-100.{{sfn|Redding|Yenne|1997|p=182|ps=}} Detailed design work continued on both variants simultaneously.

=== Introduction ===
[[File:Boeing 737-130, Lufthansa AN2056613.jpg|thumb|737-100 introduced by Lufthansa on February 10, 1968|alt=Lufthansa 737-100 in flight]]

The first -100 was rolled out on January 17, 1967, and took its maiden flight on April 9, 1967, piloted by [[Brien Wygle]] and Lew Wallick.<ref name=737_30th>{{cite web|title=Original 737 Comes Home to Celebrate 30th Anniversary|url=http://boeing.mediaroom.com/1997-05-02-Original-737-Comes-Home-to-Celebrate-30th-Anniversary|website= boeing.com|publisher=Boeing|access-date=November 18, 2014|date=May 2, 1997|archive-date=November 29, 2014|archive-url=https://web.archive.org/web/20141129031351/http://boeing.mediaroom.com/1997-05-02-Original-737-Comes-Home-to-Celebrate-30th-Anniversary|url-status=live}}</ref> After several test flights the [[Federal Aviation Administration]] (FAA) issued Type Certificate A16WE certifying the 737-100 for commercial flight on December 15, 1967.{{sfn|Sharpe|Shaw|2001|p=20|ps=}}<ref name="Type_Cert_A16WE">[http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/e038ae3ed2dbc2ae86257479004d1e57/$FILE/A16WE.pdf "Type Certificate Data Sheet A16WE."] {{Webarchive|url=https://web.archive.org/web/20080909234057/http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/e038ae3ed2dbc2ae86257479004d1e57/$FILE/A16WE.pdf |date=September 9, 2008}} ''faa.gov.'' Retrieved: September 3, 2010.</ref> It was the first aircraft to have, as part of its initial certification, approval for [[Instrument approach|Category II approaches]],{{sfn|Redding|Yenne|1997|p=183|ps=}} which refers to a precision instrument approach and landing with a decision height between {{Convert|30|and|60|m|ft|order=flip}}.<ref>{{cite news |last1=Williams |first1=Scott |title=CAT II – Category II – Approach |url=https://aviationglossary.com/cat-ii-category-ii-approach/ |website=Aviation Glossary |access-date=October 30, 2018 |date=January 18, 2009 |archive-date=October 31, 2018 |archive-url=https://web.archive.org/web/20181031005411/https://aviationglossary.com/cat-ii-category-ii-approach/ |url-status=live}}</ref> Lufthansa received its first aircraft on December 28, 1967, and on February 10, 1968, became the first non-American airline to launch a new Boeing aircraft.{{sfn|Sharpe|Shaw|2001|p=20|ps=}} Lufthansa was the only significant customer to purchase the 737-100 and only 30 aircraft were produced.{{sfn|Sharpe|Shaw|2001|p=120|ps=}}

The -200 was rolled out on June 29, 1967, and had its maiden flight on August 8, 1967. It was then certified by the FAA on December 21, 1967.<ref name="Type_Cert_A16WE" />{{sfn|Endres|2001|p=124|ps=}} The inaugural flight for United Airlines took place on April 28, 1968, from [[O'Hare International Airport|Chicago]] to [[Gerald R. Ford International Airport|Grand Rapids, Michigan]].{{sfn|Sharpe|Shaw|2001|p=20|ps=}} The lengthened -200 was widely preferred over the -100 by airlines.<ref>{{cite web |url=http://modernairliners.com/boeing-737/boeing-737-history |title=Boeing 737 History |publisher=ModernAirlines.com |access-date=August 10, 2015 |date=July 29, 2015 |archive-date=August 22, 2015 |archive-url=https://web.archive.org/web/20150822194856/http://modernairliners.com/boeing-737/boeing-737-history |url-status=live}}</ref> The improved version, the 737-200 Advanced, was introduced into service by [[All Nippon Airways]] on May 20, 1971.{{sfn|Bowers|1989|p=496|ps=}}

The 737 original model with its variants, known later as the ''Boeing 737 Original'', initially competed with SE 210 Caravelle and BAC-111 due to their earlier entry into service and later primarily with the [[McDonnell Douglas]] DC-9, then its [[McDonnell Douglas MD-80|MD-80]] derivatives as the three European short-haul single aisles slowly withdrew from the competition. Sales were low in the early 1970s<ref name="Flying blind">{{cite news |last1=Podsada |first1=Janice |title=Small local suppliers flying blind through 737 Max crisis |url=https://www.heraldnet.com/business/small-local-suppliers-flying-blind-through-737-max-crisis/ |access-date=January 17, 2020 |work=The Everett Herald |date=January 11, 2020 |archive-date=January 17, 2020 |archive-url=https://web.archive.org/web/20200117014533/https://www.heraldnet.com/business/small-local-suppliers-flying-blind-through-737-max-crisis/ |url-status=live}}</ref> and, after a peak of 114 deliveries in 1969, only 22 737s were shipped in 1972 with 19 in backlog.<!--<ref name=FG170406 />--> The [[US Air Force]] saved the program by ordering [[Boeing T-43|T-43s]], which were modified Boeing 737-200s.<!--<ref name=FG170406 />--> African airline orders kept the production running until the 1978 US [[Airline Deregulation Act]], which improved demand for six-abreast narrow-body aircraft. Demand further increased after being re-engined with the [[CFM56]].<ref name=FG170406 /> The 737 went on to become the highest-selling commercial aircraft in terms of orders until surpassed by the competing [[Airbus A320 family]] in October 2019, but maintains the record in total deliveries.<ref>{{Cite web|last=Slotnick|first=David|title=Boeing's 737 officially lost the title of world's most popular airplane. Airbus' competitor just passed it in sales.|url=https://www.businessinsider.com/airbus-beats-worlds-most-popular-plane-a320-737-2019-11|access-date=October 18, 2021|website=Business Insider|language=en-US}}</ref>

The fuselage is manufactured in [[Wichita, Kansas]], by Boeing spin-off company [[Spirit AeroSystems]], before being moved by rail to Renton.<ref>[https://www.railwayage.com/freight/bnsf-mrl-move-10000th-boeing-737-fuselage/?RAchannel=news BNSF, MRL move 10,000th Boeing 737 fuselage] {{Webarchive|url=https://web.archive.org/web/20191103185122/https://www.railwayage.com/freight/bnsf-mrl-move-10000th-boeing-737-fuselage/?RAchannel=news |date=November 3, 2019}} ''[[Railway Age]]'' February 20, 2018</ref> The [[Boeing Renton Factory|Renton factory]] has three assembly lines for the 737 MAX; a fourth is planned to open at the [[Boeing Everett Factory|Everett factory]] in 2024.<ref>{{cite news |last=Gates |first=Dominic |date=January 30, 2023 |title=Boeing to set up a new 737 MAX assembly line in Everett |url=https://www.seattletimes.com/business/boeing-aerospace/boeing-to-set-up-a-fourth-737-max-assembly-line-in-everett/ |work=The Seattle Times |accessdate=July 18, 2023}}</ref>