Rolls-Royce PLC (LON:RR.) has warned that repairing the problem of the blades on its troubled Trent 1000 engine is taking longer than expected.
More engines have been taking out of service than planned, which has strained its maintenance, repair and overhaul (MRO) capacity.
Rolls-Royce is trying to boost its MRO capability, but now expects the number of aircraft grounded because of the problem to stay in double digits until the second quarter of 2020.
Originally, the FTSE 100 group had hoped to have reduced the number of aircraft on the ground to below ten by the end of this year.
In its statement, the aero-engine maker said it deeply regretted the additional disruption the delays will cause customers.
Guidance for the cash costs of the Trent 1000 overhaul was unchanged from estimates published with its half-year figures in August.
At that time, Rolls-Royce flagged that the repairs were proceeding more slowly than predicted and would cost around £100mln more than previously forecast, taking the total expected bill to £1.6bn.