Editing Boeing 737 (section)

=== 737 Classic (second generation) ===
{{main|Boeing 737 Classic}}

The ''Boeing 737 Classic'' is the name given to the 737-300/400/500 series after the introduction of the -600/700/800/900 series of the Boeing 737 family.<ref>{{cite web |url= http://www.boeing.com/boeing/commercial/737family/facts.page |title= Boeing: Boeing 737 Facts |date= September 6, 2013 |access-date= February 7, 2015 |publisher= Boeing |archive-date= February 15, 2015 |archive-url= https://web.archive.org/web/20150215183442/http://www.boeing.com/boeing/commercial/737family/facts.page |url-status= live}}</ref> Produced from 1984 to 2000, a total of 1,988 Classic series were delivered.{{sfn|Endres|2001|p=129|ps=}}

Close to the next major upgrade of single aisle aircraft at Airbus and Boeing, the price of jet fuel reached a peak in 2008, when airlines devoted 40% of the retail price of an air ticket to pay for fuel, versus 15% in 2000.<ref>"To Save Fuel, Airlines Find No Speck Too Small." ''[[The New York Times]]'', June 11, 2008.</ref><ref>{{cite web |title=Jet Fuel Price Development |url=http://www.iata.org/publications/economics/fuel-monitor/Pages/price-development.aspx |publisher=IATA |access-date=April 10, 2015 |archive-date=April 11, 2015 |archive-url=https://web.archive.org/web/20150411084634/http://www.iata.org/publications/economics/fuel-monitor/Pages/price-development.aspx |url-status=live}}</ref> Consequently, in that year carriers retired Boeing 737 Classic aircraft to reduce fuel consumption; replacements consisted of more efficient 737 Next Generation or A320 family aircraft. On June 4, 2008, [[United Airlines]] announced it would retire all 94 of its Classic 737 aircraft (64 737-300 and 30 737-500 aircraft), replacing them with A320 family jets taken from its [[Ted (airline)|Ted]] subsidiary, which has been shut down.<ref>"UAL Cuts Could Be Omen." ''[[The Wall Street Journal]]'', June 5, 2008, p. B3.</ref><ref>{{cite web |author1=David Grossman |date=June 29, 2000 |title=Why Ted's demise is a boost for business travelers |website=USA Today |url=http://usatoday30.usatoday.com/travel/columnist/grossman/2008-06-27-demise-of-ted_N.htm |access-date=November 19, 2014 |archive-date=October 16, 2015 |archive-url=https://web.archive.org/web/20151016201845/http://usatoday30.usatoday.com/travel/columnist/grossman/2008-06-27-demise-of-ted_N.htm |url-status=live}}</ref><ref>"Airline Shares Gain Despite Losses." ''[[The Wall Street Journal]]'', July 23, 2008, p. B3.</ref> This intensified the competition between the two giant aircraft manufacturers, which has since become a [[Competition between Airbus and Boeing|duopoly competition]].

An optional upgrade with [[winglet]]s became available for the Classic and NG series.
* The 737-300 and 737-500 can be retrofitted with [[Aviation Partners]] Boeing winglets, and the 737-300 retrofitted with winglets is designated the -300SP (Special Performance).
* WestJet was to launch the 737-600 with winglets, but dropped them in 2006.<ref>{{cite web |url= http://www.boeing.com/commercial/737family/winglets/index.html |title= Next-Generation 737 Production Winglets |publisher= Boeing|archive-url= https://web.archive.org/web/20080428073227/http://www.boeing.com/commercial/737family/winglets/index.html |archive-date= April 28, 2008}}</ref>

==== 737-300 ====
[[File:N513AU in Florida, 1991.jpg|thumb|A 737-300 with larger CFM56 turbofans, introduced by USAir on November 28, 1984. This aircraft would later crash as [[USAir Flight 427]].]]
Development began in 1979 for the 737's first major revision, which was originally introduced as the 'new generation' of the 737.{{sfn|Shaw|1999|p=7|ps=}} Boeing wanted to increase capacity and range, incorporating improvements to upgrade the aircraft to modern specifications, while also retaining commonality with previous 737 variants. In 1980, preliminary aircraft specifications of the variant, dubbed 737-300, were released at the [[Farnborough Airshow]].{{sfn|Endres|2001|p=126|ps=}} This first major upgrade series was later renamed 737 Classic. It competed primarily with the MD-80, its later derivative the [[McDonnell Douglas MD-90|MD-90]], and the newcomer [[Airbus A320 family]].

Boeing engineer Mark Gregoire led a design team, which cooperated with [[CFM International]] to select, modify and deploy a new engine and nacelle that would make the 737-300 into a viable aircraft. They chose the [[CFM International CFM56|CFM56-3B-1]] [[Bypass ratio|high-bypass]] [[turbofan]] engine to power the aircraft, which yielded significant gains in fuel economy and a reduction in noise, but also posed an engineering challenge, given the low ground clearance of the 737 and the larger diameter of the engine over the original Pratt & Whitney engines. Gregoire's team and CFM solved the problem by reducing the size of the fan (which made the engine slightly less efficient than it had been forecast to be), placing the engine ahead of the wing, and by moving engine accessories to the sides of the engine pod, giving the engine a distinctive non-circular "hamster [[Cheek pouch|pouch]]" air intake.{{sfn|Endres|2001|p=128|ps=}}<ref>Sweetman, Bill, All mouth, Air & Space, September 2014, p.14</ref> Earlier customers for the CFM56 included the U.S. Air Force with its program to re-engine KC-135 tankers.{{sfn|Garvin |1998|p=137}}

The passenger capacity of the aircraft was increased to 149 by extending the fuselage around the wing by {{Convert|2.87|m|ftin|sp=us|order=flip}}. The wing incorporated several changes for improved aerodynamics. The wingtip was extended {{Convert|9|in|cm}}, and the wingspan by {{Convert|1|ft|9|in|cm}}. The leading-edge slats and trailing-edge flaps were adjusted.{{sfn|Endres|2001|p=128|ps=}} The tailfin was redesigned, the flight deck was improved with the optional EFIS (Electronic Flight Instrumentation System), and the passenger cabin incorporated improvements similar to those developed on the [[Boeing 757]].{{sfn|Shaw|1999|p=10|ps=}} The prototype -300, the 1,001st 737 built, first flew on February 24, 1984, with pilot Jim McRoberts.{{sfn|Shaw|1999|p=10|ps=}} It and two production aircraft flew a nine-month-long certification program.{{sfn|Shaw|1999|pp=12–13|ps=}} The 737-300 retrofitted with [[Aviation Partners]]' winglets was designated the -300SP (''Special Performance''). The 737-300 was replaced by the 737-700 of the Next Generation series.

==== 737-400 ====
[[File:Boeing 737-401, Piedmont Airlines AN0203147.jpg|thumb|Stretched by 10 feet (3.0 m), the 737-400 entered service in October 1988 with [[Piedmont Airlines (1948–1989)|Piedmont Airlines]]]]

The 737-400 was launched in 1985 to fill the gap between the 737-300 and the 757-200. In June 1986, Boeing announced the development of the 737-400,{{sfn|Redding|Yenne|1997|p=185|ps=}} which stretched the fuselage a further {{Convert|10|ft}}, increasing the capacity to 188 passengers, and requiring a tail bumper to prevent [[tailstrike]]s during take-off and a strengthened [[wing spar]].<ref name="rgl.faa.gov">{{cite report |title=FAA Type Certificate Data Sheet A16WE |url=http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/9c59427a20b3253686257d03004d8faa/$FILE/A16WE_Rev_53.pdf |publisher=Department of Transportation, Federal Aviation Administration |date= |access-date=July 8, 2015 |archive-date=December 25, 2016 |archive-url=https://web.archive.org/web/20161225060513/http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/9c59427a20b3253686257d03004d8faa/$FILE/A16WE_Rev_53.pdf |url-status=live}}</ref> The -400s first flight was on February 19, 1988, and, after a seven-month/500-hour flight-testing run, entered service with [[Piedmont Airlines (1948–1989)|Piedmont Airlines]] that October.{{sfn|Shaw|1999|p=14|ps=}} The last two -400s, i.e. the last 737 Classics series, were delivered to [[CSA Czech Airlines]] on February 28, 2000.<ref>{{cite press release |url= https://boeing.mediaroom.com/2000-02-28-Boeing-Delivers-737-400s-to-CSA-Czech-Airlines |title= Boeing Delivers 737-400s to CSA Czech Airlines |date= February 28, 2000 |publisher= Boeing |access-date= August 30, 2020 |archive-date= September 15, 2020 |archive-url= https://web.archive.org/web/20200915173112/https://boeing.mediaroom.com/2000-02-28-Boeing-Delivers-737-400s-to-CSA-Czech-Airlines |url-status= live}}</ref> The 737-400 was replaced by the 737-800 of the Next Generation series. The 737-400SF was a 737-400 converted to freighter, though it was not a model delivered by Boeing and hence the nickname ''Special Freighter (SF)''. [[Alaska Airlines]] was the first to convert one of their 400s from regular service to an aircraft with the ability to handle 10 pallets.<ref>{{cite web |url=http://www.alaskaair.com/content/travel-info/fleet/737-400-freighter.aspx |title=Boeing 737-400 Freighter |work=Aircraft Information |publisher=Alaska Airlines |access-date=June 29, 2011 |archive-date=January 22, 2014 |archive-url=https://web.archive.org/web/20140122165843/https://www.alaskaair.com/content/travel-info/fleet/737-400-freighter.aspx |url-status=live}}</ref> The airline had also converted five more into fixed combi aircraft for half passenger and freight. These 737-400 Combi aircraft were retired in 2017 and replaced by the 737-700F of the Next Generation series.<ref>{{Cite news|url=https://blog.alaskaair.com/alaska-airlines/fleet/combi-plane-retires/|title=The end of an era: Alaska retires unique cargo-passenger 'combi' planes|date=October 16, 2017|work=Alaska Airlines Blog|access-date=July 26, 2018|language=en-US|archive-date=March 26, 2019|archive-url=https://web.archive.org/web/20190326170156/https://blog.alaskaair.com/alaska-airlines/fleet/combi-plane-retires/|url-status=live}}</ref>

==== 737-500 ====
[[File:Boeing 737-500 (Southwest Airlines) (2389306174).jpg|thumb|A [[Southwest Airlines]] 737-500 landing in [[Harry Reid International Airport|Las Vegas]] in 2008]]

The 737-500 was offered as a modern and direct replacement of the 737-200. It was launched in 1987 by [[Southwest Airlines]], with an order for 20 aircraft,{{sfn|Shaw|1999|p=40|ps=}} and it flew for the first time on June 30, 1989.{{sfn|Shaw|1999|p=14|ps=}} A single prototype flew 375 hours for the certification process,{{sfn|Shaw|1999|p=14|ps=}} and on February 28, 1990, [[Southwest Airlines]] received the first delivery.{{sfn|Endres|2001|p=129|ps=}}

The -500 incorporated the improvements of the 737 Classic series, allowing longer routes with fewer passengers to be more economical than with the 737-300. The fuselage length of the 737-500 is {{Convert|1|ft|7|in|cm}} longer than the 737-200, accommodating up to 140<ref name="rgl.faa.gov" /> passengers. Both glass and older-style mechanical cockpits arrangements were available.{{sfn|Shaw|1999|p=14|ps=}} Using the CFM56-3 engine also gave a 25 percent increase in [[fuel efficiency]] over the older 737-200s P&W engines.{{sfn|Shaw|1999|p=14|ps=}}
The 737-500 has faced accelerated retirement due to its smaller size, after 21 years in service compared to 24 years for the -300.<ref>{{cite news|url=https://airwaysmag.com/airchive/southwest-retires-final-boeing-737-500/|title=Southwest Retires Final Boeing 737-500|work=Aircraft Information|date=September 7, 2016 |publisher=Airways Magazine|access-date=August 30, 2020|archive-date=March 7, 2021|archive-url=https://web.archive.org/web/20210307231717/https://airwaysmag.com/airchive/southwest-retires-final-boeing-737-500/|url-status=live}}</ref> While a few 737-300s were slated for freighter conversion, no demand at all existed for a -500 freighter conversion. The 737-500 was replaced by the 737-600 of the Next Generation series, though the -600 was not as successful in total orders as the -500.