Rolls-Royce has acknowledged a level of uncertainty surrounding the in-service issues of its Trent 1000 engine, and indicated that the situation will remain "dynamic" until at least next year.

Until the engine's long-term performance can be assessed during "sustained periods" between scheduled overhauls, the UK manufacturer "cannot guarantee" that no potential further technical issues will be discovered, chief executive Warren East said during a results briefing today.

East says the "identified issues" with the Boeing 787-powering engine – these centred on durability of compressor and turbine blades – were discovered in 2016-17.

While problems with intermediate-pressure turbine blades on Trent 1000 Package B and C engines have been "pretty much" resolved with the introduction of a redesigned component, subsequently disclosed issues with IP compressor blades were "not completely understood" until the first quarter of 2018, East concedes.

"We were learning what the issues were," he says.

But as "manifestation" of the IP compressor blade problem has "not evolved" since late 2017, he is confident that the manufacturer's ongoing efforts to introduce a redesigned IP compressor blade will resolve the issue.

Nevertheless, East foresees a "dynamic situation" over the next 12-18 months.

Meanwhile, R-R is working with affected 787 operators "almost on an aircraft-by-aircraft basis" to limit disruption.

Since 44 Dreamliners were parked in June as a result of maintenance to their Trent 1000s, the fleet of aircraft on ground has declined. R-R says the figure "fluctuates quite a bit" as engines come in and out of shops, and is averaging in the "high 30s" this week.