The CFM56 (that failed on the Southwest flight recently) is actually a fairly old engine design - it ran for the first time in the 1970s, and has been in servic

The CFM56 (that failed on the Southwest flight recently) is actually a fairly old engine design - it ran for the first time in the 1970s, and has been in service on the 737 for decades. Based on total run time, it's actually one of the more reliable jet engines ever created. The equivalent product for the A320NEO/737 Max is called the Leap 1A/1B. It's doing better than many of the new generation of jet engines, but it also has a flaw that requires a certain part to be replaced on all ~500 or so in-service engines.