Boeing Co is urging airlines to carry out a major retrofit on over 220 of its 777 jets in the light of a series of potentially dangerous incidents of overheating and chronic structural damage to engine parts, the Wall Street Journal reported.

The Journal said Boeing's service bulletin issued last week covers the company's 777 jets with Rolls-Royce engines and a type of thrust reverser, a device attached to the engine that helps jets slow down after landing.

Boeing did not say how much fixing the thrust reversers could cost and it is not clear whether the airlines will have to shoulder the bulk of the expense, the paper said.

The carriers reported most affected include AMR Corp's American Airlines and Delta Air Lines Inc .

A European spokesman for Boeing said he was checking on the report and had no immediate comment. No one at Rolls-Royce was immediately available for comment.

Installation of the redesigned thermal-protection system, including new insulation blankets and other cooling features, is expected to start within weeks, the Journal said, citing a Boeing spokeswoman.

(Reporting by Deepti Govind in Bangalore; Editing by David Cowell)

American Airlines