There are too many reductions to list... some are cut right to the end of the winter timetable while others are just throughout Nov, Dec and some of Jan. A few I picked up on...
LTN - ABZ down to one daily.
STN - Ljubljana reduced to 3x weekly for most of the winter
Various cuts on London - Glasgow / Edinburgh / Belfast from all bases
STN - CPH down to 2x daily for a bit (Jan?)
LGW - FCO down to 2x daily, but back to 3x by March
ALC / AGP / PMI reductions from just about everywhere
Some random cuts on LGW - GIB in Jan / Feb
Various other 1 day a week cuts here and there, and for different periods
Any others?
If this is what it takes to survive in the current climate though, then fair play to U2. They certainly aren't the first to streamline this winter and they won't be the last.