WASHINGTON, DC - The U.S. Federal Aviation Administration (FAA) has ordered immediate inspections of all Boeing 777-200 planes using Pratt & Whitney PW4000 engines.

This follows the February 20 near-catastrophe when a United 777 had its engine catch fire during a flight.

Debris from the engine fell onto a Colorado residential neighborhood.

The engine fire occurred on United Airlines flight UA328, carrying 241 passengers and crew.

Among the planned procedures by inspectors, the fans on the Pratt & Whitney engine are to undergo thermal acoustic imaging to determine whether structural failures are occurring.

"Based on the initial results as we receive them, as well as other data gained from the ongoing investigation, the FAA may revise this directive to set a new interval for this inspection or subsequent ones," the FAA said in a statement.

Following engine failure aboard a United flight in 2018, the FAA later ordered fan inspections every 6,500 cycles. A cycle is one take-off and landing.

After this latest incident, South Korea's transport ministry said it will require its country's airlines to inspect 777 fan blades every 1,000 cycles.

An airline would typically accumulate 1,000 cycles about every 10 months on a 777, according to an industry source.

The Pratt & Whitney PW4000 engines are used on 128 United 777s, representing less than ten percent of all planes.

United has now grounded all 777s using the suspect engine.

No other U.S. airline uses the Pratt & Whitney PW4000 engine.