Boeing 737 was launched in February 1965 as a logical short-rangeairplane to complement the larger Boeing 707 and Boeing 727 jetliners.

Engineering studies on short-range designs led Boeing to choose wing-mounted engines for Boeing 737 -- as opposed to the aft-mounted engines of Boeing 727 or the wing-strut mountings used on later versions of Boeing 737. Features of this configuration included a versatile Boeing 707-width body, less structural weight per passenger carried and a significant reduction in overall fuselage length. Depending on the interior configuration, the aircraft can accommodate 85 passengers in mixed class seating or 99 passengers seated six abreast.

The initial customer for Boeing 737-100 was Deutsche Lufthansa, the Germannational airline, which ordered 21 in February 1965. This was the firsttime that a Boeing airplane was sold to a foreign airline before it wasordered by an American customer.

However, production of future Boeing 737 models hinged on a United Airlines order. The fact that United already had Boeing 727s in its fleet was an important factor in a Boeing 737 每 Boeing 727 package that Boeing proposed.

Boeing offered the airline additional Boeing 727s, with an option of returning any extra Boeing 727s when Boeing 737s became available. In April 1965, United accepted the offer but wanted a larger version of the Boeing 737. The company responded by lengthening the fuselage more than 6 feet -- a 36-inch section forward of the wing and a 40-inch section aft of the wing. The stretched airplane could carry up to 124 passengers in six-abreast seating and was designated Boeing 737-200. United ordered 40.

Boeing 737-100 utilizes Pratt & Whitney JT8D-7 turbofan jet engines capable of generating 14,000 pounds of thrust, with some higher thrust JT8D units available as options. The airplanes also are equipped with an onboard auxiliary power unit. High-lift devices similar to those on Boeing 727 ensure excellent low-speed performance.

The first Boeing 737, a -100, flew April 9, 1967, followed by U.S. Federal Aviation Administration certification of both Boeing 737-100 and -200 in December of the same year after more than 1,300 hours of flight testing by a six-airplane fleet. For the first time, certification included approval for automatic approaches in bad weather under Category II conditions -- defined as 100-foot (30.5-m) ceilings and 1,200-foot (366-m) forward visibility.

The first Boeing 737-100 was delivered to Lufthansa Dec. 28, 1967 and began commercial revenue service on Feb. 10, 1968. The last Boeing 737-100 model was produced in 1969 and delivered in November that same year. Interestingly, the last Boeing 737-100 delivered was actually the first Boeing 737 Boeing produced. The aircraft had been used by Boeing as a test airplane before being delivered to NASA on July 26, 1973, for use as a test and training aircraft by the space agency. The aircraft presently is still in use with NASA. All told, Boeing delivered thirty Boeing 737-100s.

Boeing 737 is the best-selling jetliner fleet in the world. Much of the credit for this achievement belongs to Boeing 737-200, which accounted for 1,114 -- nearly one third -- of all Boeing 737s ordered.

During its production run from 1966 to 1988, versatility and reliability were keys to the popularity of the jetliner. Improved engines, better utilization of interior space, ease of maintainability and advanced avionics helped make Boeing 737-200 one of the most productive and economical airplanes in its class.

The original Boeing 737-100 and the longer-fuselage Boeing 737-200 were certificated for airline service in December 1967. Certification included approval for two-person crew operation and automatic approaches with a 100-foot ceiling and 1,200-foot forward visibility.

The first Boeing 737 -- the -100 model -- entered commercial service in Europe with Lufthansa on Feb. 10, 1968, less than one year after its first flight. On April 28, 1968, the Boeing 737 began airline service in the United States

with a Boeing 737-200 model operated by United Airlines.

Once in service, Boeing 737-200 quickly proved to be the overwhelming favorite of airline customers, and Boeing 737-100 model was discontinued after production of 30 airplanes. Depending on the interior configuration, Boeing 737-200 can accommodate 95 passengers in mixed-class seating or 124 passengers seated six abreast.

Though often operated on shorter routes, Boeing 737-200 can fly nonstop up to 2,880 statute miles (4,630 km) with a full passenger payload. A self-sufficient airplane, it can serve remote airfields without the need of ground support equipment such as jetways, electric power units and baggage conveyors.

Advanced avionics and an automatic flight control system not only provided pilots more flight information in a more concise and easier-to-use format but also, through automatic functions, reduced fuel burn by more efficient management of the plane's throttles and flight direction. The upgraded avionics also provided for safe landings under adverse weather conditions and gave pilots and ground crews more information about airplane systems.

The last Boeing 737-200 model was produced in 1971 and delivered April 5, 1971, to Indian Airlines.

In May 1971, Advanced Boeing 737-200 was introduced. This model was offered in two versions: Advanced Boeing 737-200, which seats 120 passengers in typical one-class service, and Advanced Boeing 737-200C (convertible passenger/cargo). Both were available in optional higher gross weights for increased payload or range.

Though it had the same physical dimensions as the original Boeing 737-200 model, the Advanced version incorporated aerodynamic improvements, automatic wheel brakes, more powerful engines, and greater fuel capacity, gross weight and range than its predecessors. These improvements also allowed the Advanced Boeing 737-200 to operate from airfields as short as 3,600 feet (1,100 m). Options such as low-pressure tires and gravel runway capability make it possible for Boeing 737-200 to operate from unpaved fields anywhere. Quiet engine nacelles were offered as an option. In all, the Advanced Boeing 737-200 had a 15 percent improvement in payload-range capability over its predecessor.

Deliveries of an improved engine, offering a 5 percent reduction in fuel consumption, began in late 1982. The engine, a Pratt & Whitney JT8D-15A, provides 15,500 pounds of thrust and became the standard powerplant on all Boeing 737-200s and -200Cs. A lower thrust JT8D-9A engine also was available, as well as more powerful JT8D-17A engines.

Manufacturing techniques developed for Boeing 757 and Boeing 767 became standard in Boeing 737-200, including application of special sealants and enameling of major portions of the fuselage structure to ensure corrosion protection.

Boeing 737-200 also benefited from advanced composites technology. Graphite/epoxy elevators, rudder and ailerons became standard items on Boeing 737-200s beginning with deliveries in mid-1984. These carbon fiber parts helped reduce fuel consumption because they were lighter than conventional aluminum units.

All Nippon Airways took delivery of the first Advanced Boeing 737-200 on May 20, 1971, and placed it into commercial service a month later. The last Advanced Boeing 737-200 was produced in 1988 and delivered Aug. 8 that same year to Xiamen Airlines.

The convertible cargo/passenger Boeing 737-200C incorporates an 84.5- by 134-inch (2.1- by 3.4-m) forward cargo door and a roller system in the floor. The aircraft can accept the same pallets used on conventional convertible jets (Boeing 707, Boeing 727, DC-8), permitting easy transfer of cargo loads. It can be converted in less than an hour to carry all passengers, all cargo or a combination of cargo and passengers. In the cargo configuration the "wide-body look" interior accommodates all standard-body pallets and containers without removal of interior panels and bins.

Total main-deck cargo volume is 2,730 cubic feet (81.9 m3), utilizing seven 88- by 125-inch (2.24- by 3.18-m) pallets.

The first Boeing 737-200C convertible was delivered to Wien Consolidated of Alaska on Oct. 30, 1968. The last was produced in 1985 and delivered to Markair July 5 that same year.

Boeing 737-200 and Advanced Boeing 737-200 also were delivered with an executive interior. The interior came in a wide variety of configurations depending on customer requirements. Some airplanes were delivered without any interior furnishings for customer installation of special interiors.

Boeing 737-300

Boeing 737-300 program was launched in March 1981. The market requirements for this derivative airplane became clear during the late 1970s in an environment of airline deregulation and the fierce competition that followed.

As a result of increased competition, there were changes in the way air routes were served at that time. Airplanes flew into airports operated

as hubs, then dispersed into a spoke configuration, often to short-distance destinations. Boeing 737 proved ideal for airlines operating frequent short- to medium-range routes.

A fuselage extension of 104 inches (2.6 m) allowed Boeing 737-300 to accommodate seats for up to 20 more passengers than its predecessor, Boeing 737-200 model. In mixed-class service with 36/31-inch pitch, Boeing 737-300 seats 126 passengers; in an all-tourist arrangement at 32-inch pitch, seating is 140. For inclusive-tour charter service (30-inch pitch), a maximum of 149 passengers can be carried.

From the outset, one of the main objectives of Boeing 737-300 program was to maintain commonality with the existing fleet. The airplane would use new and larger CFM56-3 engines, an advanced-technology flight deck and a common airframe. These features afforded airlines a lower investment in spares, interchangeable flight crews, and less ground support equipment and maintenance training. New aluminum alloys and composites were used to reduce the airplane's weight, and aerodynamic improvements were adapted from Boeing 757 and Boeing 767 airplanes.

Unlike its predecessor, Boeing 737-200, which was powered by Pratt & Whitney JT8D engines mounted against the underside of the wing in long, thin nacelles, the power plants for Boeing 737-300 -- as well as all subsequent versions of Boeing 737 -- are mounted forward of the wing on struts. Relocating engine accessories from the bottom of the engine to the side and flattening the bottom of the inlet lip solved the ground-clearance problem created by the larger engines. In addition, the nose wheel unit was attached 5 inches lower on the fuselage.

Besides the new engines, the flight deck of Boeing 737-300 was upgraded to make use of digital technology like that of Boeing 757 and Boeing 767 airplanes. These electronics systems provide concise flight information, which allows increased fuel efficiency and improves the airplane's ability to land in bad weather.

Boeing 737-300 also borrowed Boeing 757's interior appointments, which include large enclosed bins, galleys and lavatories located fore and aft, and a wider cabin that allows airlines to choose a larger aisle or seats or more window-seat headroom.

The first Boeing 737-300 rolled out of the Boeing Renton, Washington, plant on Jan. 17, 1984, and made its initial flight Feb. 24, 1984. That began a 9-month flight test program, during which a fleet of 3 Boeing 737-300s logged nearly 1,300 hours in the air.

Certification of Boeing 737-300 by the U.S. Federal Aviation Administration was awarded Nov. 14, 1984. First deliveries of the new aircraft occurred Nov. 28, 1984, to USAir and Nov. 30, 1984, to Southwest Airlines. Both carriers put their new aircraft into revenue service during December 1984. The British Civil Aviation Authority granted certification on Jan. 29, 1985, the same day that Orion Airways of Great Britain became the first non-U.S. customer to take delivery.

In December 1985, Boeing decided to offer a Boeing 737 twinjet with a 10-foot (3 m) fuselage stretch that would add three more economy seat rows and two more first class seats, or 21 more two-class passengers when compared with earlier Boeing 737-300.

Boeing engineers had been studying a larger Boeing 737 for a number of years -- one with a fuselage lengthened enough to bring capacity to 147 seats in mixed-class service. Airlines operating Boeing 737-300 model had been pleased with its low fuel consumption and high dispatch reliability, and they urged the development of an airplane with slightly more capacity, but one that would blend easily into existing fleets of Boeing 737s.

Airlines especially liked the fact that Boeing 737-400 is a straightforward derivative of Boeing 737-300; therefore, Boeing 737-300 pilots could be cross-qualified. Flight crews who can operate both Boeing 737-300 and -400 give airlines great flexibility in scheduling and subsequent savings in fleet operations.

Boeing 737-400 was formally launched in June 1986 to augment the fleets of carriers needing more capacity to meet traffic growth. Rollout of the first Boeing 737-400 was Jan. 26, 1988. Following an 8-month flight-test program, first delivery was Sept. 15, 1988, to kickoff customer Piedmont Airlines.

Boeing 737-400 twinjet retains basic systems commonality with -300.

Thus, it is a short- to medium-range airliner with increased passenger seating, low noise levels, low fuel consumption and high dispatch reliability.

Apart from the longer fuselage, other changes from Boeing 737-300 are engines of slightly higher thrust, strengthened wing components and landing gear, and an environmental control system (the airplane's "air conditioning") that is enlarged to handle higher passenger loads. The airplane is 119 feet 7 inches (36.4 m) long with a tail height of 36 feet 6 inches (11.1 m) and wingspan of 94 feet 9 inches (28.9 m).

The engines that power Boeing 737-400 are CFM56-3, built by CFM International, a company owned by General Electric of United States and Snecma of France. The engine is a high-bypass-ratio powerplant rated at 22,000 pounds thrust and offers a 19 percent fuel burn improvement over engines powering early models of Boeing 737 and Boeing 727. The quietness of takeoffs is surprising: generally the takeoff noise cannot be heard outside of the airport boundaries. Much of the noise reduction and low fuel consumption of Boeing 737-400 is because of this superior engine.

Other advances in Boeing 737-400 stemmed from basic design.

During development work on the airplane, Boeing kept as a goal long service life and low maintenance, as well as elimination of any excess weight in the airplane. The latest aluminum alloys are used in the structure, along with increased carbon composite parts. A special program of corrosion prevention is designed to assure customers that the airplane will maintain its original structural soundness in any operating environment.

Some operators fit additional seats into Boeing 737-400. The basic U.S. configuration is 147 seats (137 economy with 31-inch pitch between seats and 10 first class at 36-inch pitch). Other options include 159 all-economy seats at 32-inch pitch, and an inclusive-tour layout of 168 passengers at 30-inch pitch.

No matter which seating arrangement is chosen, passengers benefit from Boeing 737-400's roomy interior with large overhead stowage bins for carry-on baggage and a 20-inch (500-mm) center aisle with six-abreast seating.

With the longer fuselage, airlines gain larger cargo areas. With a total usable cargo volume of 1,373 cubic feet (38.9 m³), Boeing 737-400 still offers a freight hold accessible from the ground without ladders.

The basic airplane gross weight is 138,500 pounds (62,820 kg), with an optional high-gross-weight version of 150,000 pounds (68,040 kg). Fuel capacity is 5,311 gallons (20,105 L), expanding to 6,295 gallons (23,825 L) with two optional tanks.

Boeing 737-500 was launched on May 20, 1987, with an order for 38 airplanes from Southwest Airlines.

With a fuselage 10 inches (25 cm) longer than popular Boeing 737-200 at 94 feet 9 inches (28.9 m) and the addition of advanced technologies used in larger Boeing 737-300 and -400 models, Boeing 737-500 was designed to provide airline operators with a replacement for ubiquitous Boeing 737-200 twinjet.

Boeing 737-500 offers up to 20 percent less fuel consumption per seat than a comparably configured Boeing 737-200. It provides mixed-class seating for 110 passengers, an all-economy configuration accommodating 122 and charter seating for 132.

Engines for Boeing 737-500 are from same CFM56-3 series of powerplants offered on Boeing 737-300 and -400. This engine series is noted for its exceptional fuel efficiency, low noise and high reliability. A re-rated 18,500-pound-thrust variant of CFM56-3 is the standard offering on Boeing 737-500, with full-rated 20,000-pound-thrust version available as an option. The engines are produced by CFM International, a company jointly owned by General Electric of United States and Snecma of France.

These advanced engines assure that Boeing 737-500 is a good community neighbor at even the most noise-sensitive airports. In fact, takeoff, sideline and approach noise levels are below stringent "Stage 3" limits set by U.S. government and recommended by International Civil Aviation Organization.

Maximum takeoff weights of Boeing 737-500 range from 115,500 pounds (52 390 kg) for basic offering up to 133,500 pounds (60 560 kg) for high-gross-weight version.

The interior of Boeing 737-500 is designed for maximum comfort and efficiency. Attractive sidewall panels, contoured to make optimum use of fuselage cross section, will afford additional space at the head and elbow for window seat passengers. This, in turn, allows use of seats mounted 1 inch further outboard than on older aircraft, providing an aisle 20 inches wide (50.8 cm) instead of 18 inches (45.72 cm). The wider aisle provides enough space for passengers to step around serving carts.

Another feature in cabin is a transverse galley that spans entire width of the fuselage at the back of cabin. With lavatories installed forward of this area, the galley is clear of passenger traffic; cabin crew can work more efficiently and provide faster meal and beverage service.

Much of advanced technology developed for Boeing 757 and Boeing 767 jetliners is incorporated in Boeing 737-500.

For example, wing leading edge approximates the shape of that on Boeing 757 and Boeing 767 for improved aerodynamic efficiency. Lightweight advanced composites will be used for flight control surfaces, aerodynamic fairings and engine cowlings, similar to applications in two larger Boeing twinjets. Another similarity is in the wing skins, which utilize new weight-saving aluminum alloys.

Still more Boeing 757/Boeing 767 technology is found in flight deck. Like its larger cousins, Boeing 737-500 features a fully integrated flight management system (FMS) for automatic control and guidance of the aircraft. With optional equipment, FMS makes Category IIIA automatic landings (50-foot (15-m) decision height and 700-foot (213-m) runway visual range). As a customer option, an electronic flight instrument system is available. It features multicolor cathode ray tube displays for primary flight instrumentation and offers increased reliability compared with electromechanical units.

Several additional electronic features are basic on Boeing 737-500. An engine instrument system shows engine and hydraulic information on two light-emitting diode displays. These take place of 21 separate electromechanical instruments for greater simplicity, easier maintenance and increased reliability.

The flight management computer system incorporates a required time of arrival (RTA) feature. It is the first commercial system to add time as a fourth navigation control factor along with speed, direction and altitude. RTA provides a time window for making a departure that ensures that airplane will meet a designated time of arrival in order to avoid a holding pattern at its destination. RTA can cope with en route delays too, enabling flight crews to adjust cruise speed for maximum fuel efficiency. Workloads for pilots as well as air traffic controllers should be reduced.

Another feature is windshear detection capability. Windshear is caused by a violent downburst of air that changes speed and direction as it strikes the ground. Boeing windshear detection system alerts flight crews to the condition and provides flight-path guidance to cope with it.

A number of structural changes introduced in Boeing 737-300 and -400 also are incorporated in -500 model. These include strengthened wing; tip extensions to both the wings and horizontal stabilizers; strengthened wheels, tires and brakes; lengthened and reshaped dorsal fairing at the root of the vertical tail; and repositioned nose gear to help provide engine inlet ground clearance about the same as Boeing 737-200.

Boeing 737-500 bears a high degree of commonality with all versions of Boeing 737 series, including the original -100 and -200 models. This has been an ongoing objective in development of the various models. All versions have essentially the same handling characteristics in the air as on ground.

Pilots flying earlier Boeing 737 models do not need a new type-rating to operate Boeing 737-500. Furthermore, a substantial number of replaceable parts on Boeing 737-500 are identical to those on -300 and -400, and many are the same as on -200. This simplifies airline spares inventory and maintenance. Thus, commonality makes it easy for operators to integrate Boeing 737-500 into existing fleets.

The first Boeing 737-500 rolled out of the Renton plant on June 3, 1989. First flight occurred on June 30, 1989. The airplane received flight certification from the U.S. Federal Aviation Administration on Feb. 12, 1990, and the first delivery was made to Southwest on March 2, 1990.

A brand new wing design improved fuel capacity and increased aerodynamic efficiency. Besides flying farther and faster than earlier models, the new Boeing 737s also can fly higher than the competing Airbus 320, giving passengers a smoother ride. Airlines benefit from its altitude capability by being able to fly above bad weather, congested routes and less capable airplanes.. Next-Generation Boeing 737 designers also drew inspiration from Boeing 777, placing large displays in the flightdeck dashboard and updating the passenger cabin with contoured walls and ceilings that create a spacious feeling and greater stowage capacity than the classic Boeing Boeing 737s.

In February 2000, Boeing began offering an advanced-technology winglet made of carbon graphite as an optional feature on Boeing 737-800. The 8-foot blended winglet will allow a new airplane that already flies farther, higher and more economically than competing products to extend its range, carry up to 6,000 pounds more payload, save on fuel and benefit the environment. In May 2001, the first Boeing 737-800 with winglets made their world debut in revenue service with German Carrier Hapag-Lloyd Flu.

Boeing 737s have been allowing airlines to introduce reliable, frequent service on domestic routes and short-range international flights for more than 30 years. The newest Boeing 737s allow operators to offer the same reliable service on transcontinental and medium-range international routes. Not only will passengers notice that they now have more flights between cities, but that they have jet service to new cities and can choose to take direct nonstop flights where they used to have to make a connecting flight.

Boeing 737 - the best-selling jetliner of all time - has done more to make air travel available to more people than any other airplane. Boeing 737s have carried the equivalent of the world's population - about 6.1 billion passengers