With no explanation, label text_A→text_B with either "not_related" or "related".
text_A: Boeing 737s serve markets previously filled by MD-90 airliners.
text_B: The Boeing 737 is an American short - to medium-range twinjet narrow-body airliner .. twinjet. twinjet. narrow-body. Narrow-body aircraft. airliner. airliner. Boeing. Boeing. Originally developed as a shorter , lower-cost twin-engine airliner derived from Boeing 's 707 and 727 , the 737 has developed into a family of ten passenger models with capacities from 85 to 215 passengers .. airliner. airliner. Boeing. Boeing. Boeing 707. Boeing 727. The 737 is Boeing 's only narrow-body airliner in production , with the 737 Next Generation -LRB- -700 , -800 , and -900 ER -RRB- variants currently being built .. narrow-body. Narrow-body aircraft. airliner. airliner. Boeing. Boeing. 737 Next Generation. Boeing 737 Next Generation. Production has also begun on the re-engined and redesigned 737 MAX , which is set to enter service in 2017 .. 737 MAX. Boeing 737 MAX. Originally envisioned in 1964 , the initial 737-100 made its first flight in April 1967 and entered airline service in February 1968 at Lufthansa .. Lufthansa. Lufthansa. Next , the lengthened 737-200 entered service in April 1968 .. In the 1980s Boeing launched the -300 , -400 , and -500 models , subsequently referred to as the Boeing 737 Classic series .. Boeing. Boeing. Boeing 737 Classic. Boeing 737 Classic. The 737 Classics added capacity and incorporated CFM56 turbofan engines along with wing improvements .. CFM56. CFM International CFM56#CFM56-3B-1. turbofan. turbofan. In the 1990s , Boeing introduced the 737 Next Generation , with multiple changes including a redesigned , increased span laminar flow wing , upgraded `` glass '' cockpit , and new interior .. Boeing. Boeing. 737 Next Generation. Boeing 737 Next Generation. The 737 Next Generation comprises the four -600 , -700 , -800 , and -900 models , ranging from 102 ft to 138 ft in length .. 737 Next Generation. Boeing 737 Next Generation. Boeing Business Jet versions of the 737 Next Generation are also produced .. Boeing. Boeing. 737 Next Generation. Boeing 737 Next Generation. Boeing Business Jet. Boeing Business Jet. The 737 series is the best-selling jet commercial airliner in history .. airliner. airliner. The 737 has been continuously manufactured by Boeing since 1967 with 9,486 aircraft delivered and 4,478 orders yet to be fulfilled .. Boeing. Boeing. Assembly of the 737 is performed at the Boeing Renton Factory in Renton , Washington .. Boeing. Boeing. Boeing Renton Factory. Boeing Renton Factory. Many 737s serve markets previously filled by 707 , 727 , 757 , DC-9 , and MD-80  /  MD-90 airliners , and the aircraft currently competes primarily with the Airbus A320 family .. Boeing 707. Boeing 727. Boeing 757. DC-9. DC-9. MD-80. MD-80. MD-90. MD-90. Airbus A320 family. Airbus A320 family. As of 2006 , there were an average of 1,250 Boeing 737s airborne at any given time , with two departing or landing somewhere every five seconds .. Boeing. Boeing
related.