The engines on the ANA planes, Trent 1000s, were supplied by Rolls-Royce (RR.L), which said it was replacing a component on a number of its engines.

ANA (9202.T), the launch customer for the 787, the world's first passenger jet built mainly from lightweight carbon fibre, said the action stemmed from a flawed process that could leave part of its UK-manufactured engines vulnerable to early corrosion.

The airline grounded five of its 11 Dreamliners, but three of the twinjet airplanes have been fixed and are flying again. The other two are waiting for parts from Rolls-Royce and could be out of action for a few weeks, an ANA spokesman said.

The glitch is the latest disruption to Boeing's flagship jet as the Chicago-based company recovers from a series of production delays that have come to typify the latest models being produced by Boeing (BA.N) and its European rival, Airbus (EAD.PA).

"The extent of the issue with ANA appears relatively minor at this stage, given that (three) of the aircraft have already returned to service," said RBC Capital Markets analyst Rob Stallard in a note on the incident.

Alex Hamilton, managing director with boutique investment firm EarlyBirdCapital, said he didn't think Boeing share weakness was tied to the ANA announcement, as the broader market sold off.

"My guess is the problem is fixable," Hamilton said.

Shares of Rolls-Royce fell 2.7 percent, while Boeing (BA.N) was down 1.5 percent in afternoon trading in New York. Shares of General Electric Co (GE.N), which offers an alternative engine for the 787, were up nearly 1 percent on Monday, outperforming the broader market.

The 787 engine problem involves a gearbox supplied by Hamilton Sundstrand, part of U.S. conglomerate United Technologies (UTX.N), but for now is contained to one batch.

Two people familiar with the matter said concerns over corrosion came to light during endurance testing in the UK on one of the Trent 1000 engines designed by Rolls-Royce.

During the ground test, corrosion was discovered on part of the gearbox used to drive ancillary systems. Investigators traced this to a new manufacturing process that was immediately reversed, the people said, asking not to be named.

Boeing said it was aware of the findings made by Rolls during engine testing that revealed the corrosion.

"We don't expect timing of any deliveries to be affected by this," Boeing's Scott Lefeber, a spokesman with 787 Communications, said by email.

"The replacement is expected to be complete in the days ahead," Boeing added in a statement. "No airplanes will be delivered with affected parts."

SUSPECT BATCH

Boeing said that currently, All Nippon is the only customer operating 787s with Rolls-Royce engines.

Of the 859 Dreamliners that have been ordered or delivered at this point, Rolls-Royce engines have been selected for about 228 planes, while General Electric engines have been chosen for 370 planes, according to Boeing data. Rolls spokesman Richard Hedges said by email there were 287 firm orders on hand for 787s with Trent 1000 engines.

"We have seen no such problems with our 787s. But we have found out that out of the eleven 787s we own, five of them are carrying those parts," Japan's ANA said in a statement. "For those five aircraft, we have switched them with other aircraft and are continuing to operate the flights."

A total of 17 engines contain gear boxes from the same suspect batch as the one used in the endurance test, eight of which have been delivered to ANA, industry sources said.

"We have identified that a component on Trent 1000 engines fitted to Boeing 787 Dreamliners has a reduced service life. As a proactive measure, this component is being replaced in a number of engines," a Rolls-Royce spokesman said.

United Tech's Hamilton Sundstrand arm said it was working with the other aerospace suppliers to solve the problem.

As of end-June, only Japanese carriers were operating the 787 Dreamliner, which entered service with ANA in October.

Japan Airlines, which has four Boeing 787s in its fleet, uses engines built by GE and therefore does not face problems similar to those affecting ANA, said Seiji Takaramoto, a Japan Airlines spokesman.

GLITCHES

The grounding the five Dreamliners by ANA is but one of several problems with aircraft that have delayed production and have come to typify flaws in new jetliners made by Boeing and Airbus.

In November, ANA reported a landing gear problem weeks after taking delivery of the first $194 million Dreamliner. .

A blowout on a different type of Rolls-Royce engine on the Airbus (EAD.PA) A380 in November 2010 led to delivery bottlenecks for the world's largest passenger plane as engineers swapped dozens of engines on the production line.

Rolls competes with GE to power both the A380 and the 787 Dreamliner. (Additional reporting by Tim Kelly, Scott Malone, Karen Jacobs; Writing by Sarah Young, Tim Hepher; Editing by James Regan, David Cowell and Steve Orlofsky)

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