The Federal Aviation Administration(FAA) last week required US airlines to inspect General Electric Engines on Boeing 787 Dreamliner and 747-8 aircraft that experience Icing problems which could lead to loss of thrust.

Reuters reported that FAA also required airlines to prohibit pilots from flying into high-attitude, icy weather conditions, noting that the decision to issue an airworthiness directive had been expected.

The agency said that in certain kinds of high-attitude thunderstorms, ice crystals entered and damaged the engines, causing temporary loss of thrust or in some cases increased vibration with no loss of thrust, while the problems affected nine flights and in two cases involving 747-8s it affected two of four engines.

FAA said its concern was that “unrecoverable thrust loss” on multiple engines could lead to a forced landing while General Electric noted that there had been no unrecoverable thrust loss in any of the nine incidents.

The directive is effective immediately and requires airlines to inspect General Electric GEnx engines if the “engine thrust” indicator appears in flight.

The FAA said its order only applies to 14 aircraft operated by US airlines.  Foreign aviation regulators typically follow the FAA’s lead.

Recently, Boeing and GE said they had alerted airlines about the risk of engine icing and the loss of thrust that could result and were working with them to resolve it.

Boeing and GE-had said there were six incidents in which icing occurred but the FAA’s higher tally included three incidents in which the engines “experienced a vibration during the ice-crystal storms but didn’t lose any thrust” GE Aviation spokesman Rick Kennedy said.

The issues occurred with GEnx 2B engines on Boeing 747-8 passenger and 747-8F freighter planes and it also occurred on GEnx-IB engines on 787-8s.

Japan Airlines has said it is replacing 787s on two routes because of the problem while United Airlines, the only US carrier currently flying the 787, said it was not making changes because of the issue.

Atlas Air which flies 747-8F freighters in the US, said it was alerted to the problem by Boeing on November 14, and had already taken steps to avoid the weather condition.  It expected only minimal impact on Atlas and its customers, spokeswoman Bonnie Rodney said.

GE said it has a software fix and will put it into effect early next year.

The regulator has not called the engines defective and that the situation occurs only when “encountering weather conditions at 40,000 feet for which the engines were not tested at certification”.  Kennedy stated.

“We had encountered a similar situation with our CF6 engine in the 1990s and early 2000s, and we successfully resolved the issue with a modification to the control system”, he added.