Britain's best known engineering company has been hit by a problem with a compressor in the Trent 1000 package C engine that is not lasting as long as expected, grounding planes, forcing inspections and angering airline clients.
The engine powers Boeing's 787 Dreamliner jet.
On Monday it said it had now found the same issue on a "small number of high life Package B engines", requiring a one-off inspection of the B fleet and sending its shares down 1 percent.