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The Boeing 737 Classic are narrow-body airliners produced by Boeing Commercial Airplanes, the second generation of the original Boeing 737-100/-200. Development began in 1979 and the first variant, the 737-300, first flew in February 1984 and entered service in December of that year. The stretched 737-400 first flew in February 1988 and entered service later that year The shortest variant, the 737-500, first flew in June 1989 and entered service in 1990.
The 737-400 design was launched in 1985 to fill the gap between the 737-300 and the 757-200, and competed with the Airbus A320 and McDonnell Douglas MD-80. It stretched the 737-300 another 10 ft (3.05 m) to carry up to 188 passengers. It included a tail bumper to prevent tailscrapes during take-off (an early issue with the 757), and a strengthened wing spar. The prototype rolled out on January 26, 1988, and flew for the first time on February 19, 1988.