Boeing Co was planning to replace engine covers on its 777 jets months before a pair of recent serious failures, the Wall Street Journal reported on Thursday, citing an internal Federal Aviation Administration document.

The U.S. Federal Aviation Administration (FAA) on Tuesday ordered immediate inspections of the 777 planes with Pratt & Whitney PW4000 engines before further flights, after an engine failed on a United Airlines flight on Saturday.

The planemaker and the FAA had been discussing potential fixes for about two years, according to the Journal's report, following earlier engine failures on a 777 operated by United and a Southwest Airlines 737 jet in 2018.

Boeing did not immediately respond to Reuters' request for comment.

United, the only U.S. operator of the older PW4000-powered 777s, had temporarily grounded its fleet before the FAA announcement.