The explosion of an engine on a Boeing 737 aircraft that resulted in the death of a Southwest Airlines passenger has prompted the US Federal Aviation Administration (FAA) to call for an emergency inspection of some such engines currently in service.

The April 20, 2018 emergency airworthiness directive from the FAA orders ultrasonic inspection for cracks in the fan blade dovetail of CFM International S.A. Model CFM56-7B engines, and removal of any cracked fan blades.

The FAA required that the inspections be conducted within 20 days.

The order applies to CFM56-7B engines with more than 30,000 cycles (engine startup-to-shutdown sequences). Forbes reports that the order affects 680 engines in use worldwide, including 352 in the US.

The manufacturer, CFM, followed up by recommending that engines with 20,000 cycles be inspected by the end of August 2018, and that reinspection take place every 3,000 cycles thereafter.

A fractured fan blade caused the left engine on Southwest flight 1380 from New York’s LaGuardia International Airport to Dallas to partially disintegrate, throwing debris into the airframe, breaking a window, and causing cabin depressurization. One passenger was killed after being partially sucked out of the window.

Southwest has been cancelling about 40 flights a day to comply with the inspection order.