737-400和737-300属于波音737 Classic时代的产品，较737-800（属于737 NG时代）老旧很多，维修保养成本偏高。龙浩的这些飞机的机龄大多在26年左右 ...

Before the 737 NG, Southwest operated the 737 Classic series, which included the 737-300 and 737-500. These aircraft ...