In the mid 1960's, Boeing decided to develop a jet, smaller than the B 727. This segment was still missing in the Boeing aircraft family. The DC9 and BAe 1-11 were the only other competitors at this time. The big advantage for Boeing was the know how of the very successful B 727. Many "old" parts of the B 727 fuselage could be used in the new aircraft. Nevertheless, they decided for a different approach to the B 737 project: The two engines were not located at the tail unit anymore, but under the wings, which made the B 737 lighter and brought a better center of gravity. The long and slim Pratt & Whittney engines were installed right underneath the wings, to assure good aerodynamics. This way, also the body could be as low as the DC9's body, allowing easy access at smaller airports.
As well as the B 737, the new DC9-30 version was warmly expected by the airlines. The fight for orders seemed to be won by Douglas, when Eastern decided in favor of the DC9-30. When the German Lufthansa threatened to order DC9's, Boeing decided to go into production with only 21 Lufthansa orders for the B 737-100. Two month later, United also decided for the new Boeing aircraft, but needed a higher passenger capacity. The new version was 1,93 m longer and was called B 737-200.
The first B 737-100 flew on April 9th, 1967.The first B 737-200 followed in June and was to become the most successful version. Boeing also offered a B 737-200 QC version that allowed a fast change from a passenger to a cargo aircraft with a side door and the seats on pallets. The advanced B 737-200 was build for less developed countries with small and unprepared runways. It featured a stronger body to allow more engine thrust and a higher fuel capacity. Also, a new flap system allowed slower approaches. Boeing even offered skids and nozzles, which prevented engine damage when operating from dirt runways.
Slowly, the B 737 could take over the DC9. In the early 1980's, huge orders came from many European and Nortamerican airlines, such as Lufthansa and British Airways. But also smaller Northmerican airlines could now operate freely due to the US deregulation act and by 1987, the B 737 became the best selling airliner in history.
The B 737 was constantly improved and in 1981, the B 737-300 was introduced. To maintain the low body with all it's advantages, the new General Electric engines had to be changed in order to fit below the wings. The weight of the heavier engines could be compensated by new materials used to build the fuselage and wings. The wings were also new: They were longer and a new flap system could even reduce the take off speeds. This way, Boeing could ensure that the new B 737-300 is able to operate from the same airports as the older -200. The success encouraged Boeing to think about new versions, the first of which being the stretched B 737-400 in 1988. It is 3,05 m longer than the -300 and could now fit up to 170 passengers. As a substitute for the old -200s, in1989, Boeing introduced the B 737-500, seating up to 132 passengers.
The newest versions feature longer wings and a higher tail unit: The B737-700 seats as many passengers as the -300 (<149) but offers a higher range. The demand for a 737 with the small passenger capacity of the -500 (<132) with a bigger range lead to the B737-600, which had it's inaugural flight on January, 22nd, 1998. The longest version, the -800, seats up to 189 passengers and this way makes it a direct competitor to the Airbus A 320-family.
But Boeing already works on the B737-900, which will be another 3m longer than the -800.
Based on the B737-700's fuselage, strengthened wings and landing gear from the larger and heavier 737-800, Boeing developed the BBJ, the Boeing Business Jet. It can easily be distinguished from all the other B737 when looking at the wings: The BBJ is equipped with big winglets, allowing the aircraft to fly over a max. distance of 6.200 nautical miles, 11.475 kilometers!
In the near future, these big winglets will also be installed on the B737-800. The first airline to fly on the new winglets will be the German Hapag Lloyd. The winglets will increase the range by reducing drag and fuel consumption.

737-300 Technical Characteristics Passengers Typical 3-class configuration Typical 2-class configuration Typical 1-class configuration N/A 128 149 Cargo* 1,068 cu ft (30.2 cu m) Engines maximum thrust General Electric CF56-3 22,000 lb (9,979 kg) Maximum Fuel Capacity 5,311 U.S. gal (20,105 L) Maximum Takeoff Weight 138,500 lb (62,820 kg) Maximum Range 2,595 statute miles (4,175 km) Typical Cruise Speed at 35,000 feet 0.745 Mach 495 mph (797 km/h) Basic Dimensions Wing Span Overall Length Tail Height Interior Cabin Width 94 ft 9 in (28.9 m) 109 ft 7 in (33.4 m) 36 ft 6 in (11.1 m) 11 ft 7 in (3.53 m)

In the mid 1960's, Boeing decided to develop a jet, smaller than the B 727. This segment was still missing in the Boeing aircraft family. The DC9 and BAe 1-11 were the only other competitors at this time. The big advantage for Boeing was the know how of the very successful B 727. Many "old" parts of the B 727 fuselage could be used in the new aircraft. Nevertheless, they decided for a different approach to the B 737 project: The two engines were not located at the tail unit anymore, but under the wings, which made the B 737 lighter and brought a better center of gravity. The long and slim Pratt & Whittney engines were installed right underneath the wings, to assure good aerodynamics. This way, also the body could be as low as the DC9's body, allowing easy access at smaller airports. As well as the B 737, the new DC9-30 version was warmly expected by the airlines. The fight for orders seemed to be won by Douglas, when Eastern decided in favor of the DC9-30. When the German Lufthansa threatened to order DC9's, Boeing decided to go into production with only 21 Lufthansa orders for the B 737-100. Two month later, United also decided for the new Boeing aircraft, but needed a higher passenger capacity. The new version was 1,93 m longer and was called B 737-200. The first B 737-100 flew on April 9th, 1967.The first B 737-200 followed in June and was to become the most successful version. Boeing also offered a B 737-200 QC version that allowed a fast change from a passenger to a cargo aircraft with a side door and the seats on pallets. The advanced B 737-200 was build for less developed countries with small and unprepared runways. It featured a stronger body to allow more engine thrust and a higher fuel capacity. Also, a new flap system allowed slower approaches. Boeing even offered skids and nozzles, which prevented engine damage when operating from dirt runways. Slowly, the B 737 could take over the DC9. In the early 1980's, huge orders came from many European and Nortamerican airlines, such as Lufthansa and British Airways. But also smaller Northmerican airlines could now operate freely due to the US deregulation act and by 1987, the B 737 became the best selling airliner in history.

The B 737 was constantly improved and in 1981, the B 737-300 was introduced. To maintain the low body with all it's advantages, the new General Electric engines had to be changed in order to fit below the wings. The weight of the heavier engines could be compensated by new materials used to build the fuselage and wings. The wings were also new: They were longer and a new flap system could even reduce the take off speeds. This way, Boeing could ensure that the new B 737-300 is able to operate from the same airports as the older -200. The success encouraged Boeing to think about new versions, the first of which being the stretched B 737-400 in 1988. It is 3,05 m longer than the -300 and could now fit up to 170 passengers. As a substitute for the old -200s, in1989, Boeing introduced the B 737-500, seating up to 132 passengers. The newest versions feature longer wings and a higher tail unit: The B737-700 seats as many passengers as the -300 (<149) but offers a higher range. The demand for a 737 with the small passenger capacity of the -500 (<132) with a bigger range lead to the B737-600, which had it's inaugural flight on Janurary, 22nd, 1998. The longest version, the -800, seats up to 189 passengers and this way makes it a direct compeditor to the Airbus A 320-family. But Boeing already works on the B737-900, which will be another 3m longer than the -800. Based on the B737-700's fuselage, strengthened wings and landing gear from the larger and heavier 737-800, Boeing developed the BBJ, the Boeing Business Jet. It can easily be distinguished from all the other B737 when looking at the wings: The BBJ is equipped with big winglets, allowing the aircraft to fly over a max. distance of 6.200 nautical miles, 11.475 kilometers! In the near future, these big winglets will also be installed on the B737-800. The first airline to fly on the new winglets will be the German Hapag Lloyd. The winglets will increase the range by reducing drag and fuel consumption.