Credits to @XAircraftManufacturer for the original plane

Wikipedia

The Boeing 737 Classic is a series of narrow-body airliners produced by Boeing Commercial Airplanes, the second generation of the Boeing 737 series of aircraft. 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.[12] It included a tail bumper to prevent tailscrapes during take-off (an early issue with the 757), and a strengthened wing spar.[9] The prototype rolled out on January 26, 1988, and flew for the first time on February 19, 1988.

The aircraft entered service on September 15, 1988, with launch customer Piedmont Airlines (25 aircraft ordered).[1]

The last two Boeing 737-400s, the last Boeing 737 Classics, were delivered to CSA Czech Airlines on February 28, 2000.[13] The 737-400 was replaced by the 737-800 in the Boeing 737 Next Generation family.