Originally Posted by mutt
I wonder if the airlines can statistically show that their engine maintenance costs are higher in the winter season
The maintenance benefit is obtained by reducing engine hot section temperatures when conditions permit. At wintertime ambient temperatures the engine operates anyway at temperatures well below the limiting gas temperature. Therefore the benefit of FLEX/ATM/derate is in the area of 'diminishing returns' and possibly almost nil..
EDIT:: Derating beyond 25% has no benefit and is just silly, IMO.