The Boeing 737 as a family is not being retired; in fact, it remains the backbone of the global short-to-medium haul aviation market. However, specific older "generations" of the 737 are being phased out. The 737 Original (-100, -200) and 737 Classic (-300, -400, -500) models are now quite rare in major airline fleets and are mostly seen in cargo operations or with regional carriers in developing markets. Most major airlines are currently transitioning from the 737 NG (Next Generation) series to the more fuel-efficient 737 MAX family. While the 737 has faced significant scrutiny due to technical issues in recent years, Boeing continues to produce the MAX 8, 9, and 10 models to meet massive demand from carriers like Southwest and Ryanair. So, while you might stop seeing the "classic" versions with the older, smaller engines, the silhouette of the 737 will remain a constant sight at airports for many decades to come as it evolves with new technology.