National Transportation Safety Board investigators inspect the engine that exploded on a Southwest Airlines flight on Tuesday. (NTSB)

The Federal Aviation Administration on Wednesday ordered inspections of the type of engine that exploded Tuesday on Southwest Airlines flight 1380.

The FAA said it will issue an Airworthiness Directive (AD) within the next two weeks that will require inspections of certain CFM56-7B engines. The directive requires an ultrasonic inspection of fan blades when they reach a certain number of takeoffs and landings. Any blades that fail the inspection will have to be replaced, the FAA said in a statement.

The agency had already issued an advisory for such inspections; the AD makes them mandatory.

The FAA said it is supporting the National Transportation Safety Board in its investigation into Tuesday’s explosion and “is in communication with the manufacturers and airlines on whether any further safety steps or amendments are needed.”

The NTSB said Wednesday it will examine whether metal fatigue caused an engine fan to snap midflight aboard the plane, spraying shrapnel and causing a cabin window to be blown out. One passenger died.

The FAA has been aware of the problem since a similar incident with a Southwest Airlines plane almost two years ago, and the agency had already begun implementing measures to require more frequent inspections.

On Aug. 27, 2016, a Southwest flight from New Orleans to Orlando was flying at cruising altitude when one of its two engines disintegrated, causing a gash in the fuselage. Passengers on that flight said their experience mirrored that of those on board Tuesday’s flight from New York’s LaGuardia Airport to Dallas. They heard “a loud boom and smoke trailing from the left engine, and saw metal flapping after the smoke cleared.”

Flight 1380 made an emergency landing at Philadelphia International Airport.

No one was injured on the 2016 flight, but the plane made an emergency landing in Pensacola, Fla. The FAA responded 10 months later with a recommendation that airlines use ultrasound to inspect their engine fan blades. Though most airlines have complied with that counsel, the agency thought the matter significantly urgent that it has begun the laborious federal process to mandate that every airline carry out the inspections.

Southwest CEO Gary Kelly said that the plane involved in Tuesday’s incident had undergone an inspection two days before the explosion, but he said he was not aware of the nature of that inspection or whether it included a specific inspection of that engine.

Kelly said the plane had flown 10,000 of the 40,000 trips the airline allows between engine overhauls. Southwest flies a fleet made up entirely of Boeing 737s, and all of them are equipped with the General Electric-built CFM56 engine.

“There’s no information that there were any issues with the airplane or the engine,” Kelly said Tuesday night.

One expert said that if the plane had made 10,000 trips, then it was due under the FAA advisory for a an ultrasound engine inspection after 5,000 more trips. He said that after a second incident with a GE CFM56 engine, the FAA might want to reconsider whether engines should be tested for metal fatigue more frequently than after every 15,000 trips.

“Based on the latest events, it’s apparent that we should look at these engines much sooner than we thought,” said the individual, who is familiar with the investigation and asked not to be named to speak candidly. “If this problem manifested itself at 10,000 [trips], then that’s going to be the new floor [for testing]. That’s the logical conclusion to draw, but of course it will depend on the evidence.”

Southwest said that it would speed up its existing engine inspection program after Tuesday’s explosion. In a statement released Wednesday, Southwest said: “The accelerated inspections are being performed out of an abundance of caution and are expected to be completed over the next 30 days. The accelerated checks are ultrasonic inspections of fan blades of the CFM56 engines.”

GE said the inspections would be expedited with the help of 40 GE technicians.  The inspections are expected to take about a month, a GE spokesman said Wednesday.

While the NTSB investigation precluded it from commenting on the explosion, GE, in its statement, defended the safety record of its engine.

The company lauded the CFM56-7 engine fleet, which powers nearly 7,000 planes across the globe, for what it called “an outstanding safety and reliability record” since launching in 1997.

“The engine family has accumulated more than 350 million flight hours as one of the most reliable and popular jet engine models in airline history,” GE said.