The FAA order applies to 43 planes flown by US carriers, but there are 176 aircraft operated by 29 airlines around the world that may be susceptible.

Airlines flying Boeing's 787 Dreamliner jets with the latest General Electric engines were ordered to repair them, or swap out at least one with an older model, in an urgent safety directive issued after an inflight failure.

A GEnx-1B PIP2, part of a family of engines plagued by issues related to icing, suffered "substantial damage" in the January 29 incident, when ice on the fan blades broke loose, the US Federal Aviation Administration said in an order published on Friday in the Federal Register.

"The potential for common cause failure of both engines in flight is an urgent safety issue," the FAA said in its order.

The GEnx, a high-efficiency engine developed for wide-body aircraft, has faced earlier issues with icing. In 2013, the FAA ordered airlines to avoid flying 787 and 747-8 planes equipped with the GE engines near thunderstorms in high-altitude cruise flight. Even in those sub-freezing temperatures, moisture from the storms could enter the engines and form dangerous ice, the FAA said.

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The latest issue is unrelated to the 2013 situation. The incident occurred at 20,000 feet (6096 metres) altitude, which was lower than previous icing issues encountered by the engine model.

Jet engines are critical to GE as the company sheds the bulk of its finance arm to focus on industrial manufacturing. GE Aviation, its largest division, generated sales of US$24.7 billion in 2015, or about 21 per cent of the company's total revenue.

Airlines operating 787s with GE engines have 150 days to make sure that they have made repairs or have installed at least one older version of the GEnx engine on each plane so that they won't risk losing power in both, the FAA said. The older GEnx model isn't as susceptible to damage from icing.

Airlines must also instruct pilots within seven days how to prevent engine icing while flying above 12,500 feet. When pilots suspect ice may be forming, they have to momentarily add power to each engine once every five minutes, the FAA said.

"We see it as an operational issue and we want to correct it," Rick Kennedy, a company spokesman, said in an interview.

WORK UNDER WAY

The FAA order applied to 43 planes flown by US carriers. While the FAA's order applies only to US operators, other nations typically follow the FAA's lead on safety issues.

There are 176 aircraft operated by 29 airlines around the world that may be susceptible, according to the FAA. Kennedy said GE plans to address the issue by September. Engines in production also are being altered.

Engines can be fixed by shaving off a small amount of metal from the case surrounding the fan, giving the blades more clearance to prevent the rubbing that caused the damage in January, Kennedy said. The repair can be completed without removing the engine from the plane, he said.

GE and Boeing have been investigating the issue and are working with FAA to resolve it, Boeing spokesman Doug Alder said in an emailed statement. GE's recommended actions were given to airlines on April 1, Alder said.

"Work mandated by the AD is already well under way with more than 40 engines complete," he said, referring to the FAA's airworthiness directive.

United Airlines is the largest US operator of the 787, with 28 of the carbon-fibre jets delivered to date, according to Boeing's website. United hasn't had a problem with its 787s and is "immediately complying with all FAA and manufacturer directives," spokesman Charles Hobart said in an email.

American Airlines has taken delivery of 15 of the planes. Dozens of carriers around the world have taken delivery as well.

STEADY PERFORMER

The GEnx, developed from the earlier GE90 turbofan engine, is one of the marquee products for GE Aviation. The company also makes power plants for narrow-body aircraft through its CFM International joint venture with Safran SA.

After a troubled entry marred by supply chain issues and battery fires that grounded the global fleet, the 787 Dreamliner has gained a reputation as a steady performer. Boeing officials have touted dispatch reliability that is now about 99 per cent of flights, second-only to the 777 among long-range jets.