The order, announced on Friday, impacts 680 CFM56-7B engines worldwide, 352 of which are in the United States. Those numbers represent a fraction of the 14,000 CFM56-7B engines are in operation today, according to engine manufacturer CFM International, a joint venture between GE and Safran Aircraft Engines.

The CFM56-7B, which first entered service on the Boeing 737 in 1997, is considered the workhorse of the airline industry. The engine is in use by a number of airlines.

On Tuesday an engine exploded and forced pilots of Southwest Airlines Flight 1380 to make an emergency landing at Philadelphia International Airport. The flight was carrying 144 passengers and five crew members.

When the engine exploded a fan blade broke loose and broke a window on the plane. The female passenger died after she was partially sucked through the window.

It was the first fatality on a U.S. airline in nine years that was the result of an accident.

The FAA said the directive is based on information gathered from the investigation of the Southwest Airlines engine failure, as well as a safety bulletin issued Friday by CFM International. The company called for inspections of fan blades on long-service engines.

Airlines were ordered to inspect CFM56-7B engines with more than 30,000 total cycles. The FAA said the inspection must be complete within 20 days.

CFM went a step further and also recommended inspections by the end of August for fan blades with 20,000 cycles, and inspections to all other fan blades when they reach 20,000 cycles. CFM said Friday operators should repeat the inspection every 3,000 cycles, the equivalent of about two years in airline service.

CFM noted that more than 150 of these engines have already been inspected. Inspections recommended by the end of August for fan blades with 20,000 cycles will impact an additional 2,500 engines, CFM said.