Despite its entry into service back in 1968 (with air carrier Lufthansa), the Boeing Model 737 continues to fly high today (2018). Over 10,000 aircraft in the series have been built (March 2018) with production running from 1966 to the present day. The success of the model has led to a bevy of variants being realized that includes several military platforms for various global services (including the United States). At one point in its career, the Model 737 marked the world's best-selling airliner - a reason why it continues in widespread service today (2018).
The Model 737 was originally developed as a narrow-body passenger-hauler for the short-to-medium-ranged airliner market. Born from the framework of the Model 707 and Model 727, the Model 737 was intended to provide Boeing with the ability to offer a reliable, moderate-cost performer at every level of global interest. Engineers developed a conventional, tube-shaped passenger-hauler with low-mounted wing mainplanes, tricycle landing gear, and a single-finned tail unit. Each mainplane sported an underslung engine nacelle designed to give the aircraft the necessary range, power, and performance for the short-to-medium-range marketplace. For its construction, the Model 737 relied on up to 60% commonality of parts between its sister design - the Model 727.
A first-flight of a Model 737 prototype was recorded on April 9th, 1967 and, following the requisite certifications period, the type was introduced with West Germany's air carrier Lufthansa on February 10th, 1968. The initial production model became the Model 737-100 with, as its designation suggests, seated up to 100 passengers. This entry was unveiled in February of 1965. Production was limited to just 30 airframes before attention turned to the dimensionally larger, stretched Model 737-200.
The 737-100 carried 2 x Pratt & Whitney JT8D-5, D-7, D-9, or D-17 engines varying in thrust from 14,000lb to 16,400lb each unit. The 737-200 also carried this engine.
The Model 737-200 was also unveiled back in 1965 and followed into service in April of 1968 with carrier United Airlines. The Model 737-200 "Advanced" became an improved form of the base 737-200 offering. This model was launched with Japan's All Nippon Airways in May of 1971 and sported uprated engines, increased fuel capacity and operational ranges, and automatic wheel braking systems among other qualities. Another model in this series was the 737-200C (Cargo) which added a dual ("combi") functionality - the aircraft serving passengers and cargo as needed by the operator. The United States Air Force (USAF) took on a stock of 19 Model 737-200 as well, designated as "T-43" and used in the aviation navigation role. An offshoot of this model was the "CT-43" which proved useful in USAF passenger hauling routes. The "NT-43A" was a one-off test bed for various radar fits.
The Model 737 "Classic" covered the 737-300, 737-400, and 737-500 series - second-generation forms of the Model 737. The line was established after the arrival of the 737-600, 737-700, 737-800, and 737-900 series. Nearly 2,000 aircraft were produced of all types from 1984 into 2000.
The 737-300, -400, and -500 all carried the CFM56-3 turbofan engine of 20,000 to 23,500lb thrust each unit. The 737-600, -700, -800, and -900 series were all given the CFM56-7 turbofan engine of 20,000lb to 27,000lb thrust output (each).
The Model 737 "Next Generation" (NG) was brought online in the 1990s to better compete with the French Airbus offering of the A320 (detailed elsewhere on this site). This initiative produced the 737-600, -700, -800, and -900 series mentioned above. Total production has since surpassed over 6,550 units as the company attempted to maintain its edge in the marketplace. The United States Navy (USN) has adopted the P-8 "Poseidon" for its future over-water maritime needs - this aircraft is built upon the framework of the Model 737NG.
The Model 77-33 was a modified business jet version of the Model 737-300. These were succeeded by the Boeing Business Jet (BBJ) with increased range and elements borrowed from both the 737-700 and 737-800 series. A first-flight was recorded in September of 1998. The line was then followed by the Boeing Business Jet 2 (BBJ2), based in the 737-800 mark, that increased internal volume at the expense of operational range. First-deliveries were had in February of 2001. A third iteration of the BBJ appeared as the Boeing Business Jet 3 (BBJ3) and this was built from the Model 737-900ER (Extended Range) product. Again more internal volume was granted while range was increased.
The Model 737-800BCF, its program launched in 2016, was developed into a dedicated freighter as the "Boeing Converted Freighter" (BCF). This program involves the conversion of older, aging passenger haulers to a freighter standard. First deliveries were had in 2018.
In another attempt to match the Airbus threat pound-for-pound, the Model 737 MAX was established - its direct competitor becoming the A320neo (detailed elsewhere on this site). The program was launched in August of 2011 with Southwest Airlines becoming its launch customer in May of 2017. The MAX series encompasses the MAX7, MAX8, MAX9, MAX10, business derivatives, and the MAX200.
The Model 737 MAX-7, -8, -9, and -10 all carry the CFM LEAP-1B turbofan engine offering up to 29,300lb of thrust each unit.
Heading into 2018, the Model 737 series has seen a healthy overall total of 14,725 units committed to/delivered with some 4,648 airframes still on order. Peak production was seen in 2017 with 529 units. 320 deliveries were made in 1999, the most in a calendar year for the aircraft.
Beyond its obvious civilian marketplace value, the Model 737 has proven a popular product for many militaries of the world - from Argentina and Australia to Thailand and Turkey.