Crewing
I believe that one or two outfits cancel flights with joyfull abandon at the slightest wiff of slots associated with any form of industrial action. Been chatting this through with an ops bod it would appear that the slots arent really that bad its just that certain outfits have close to zero crewing cover to handle any delays. One I know of regularly has no standby cover at all at a couple of bases. A colleague called in sick, flight delayed nearly 4 hours. Ac flown from other base with full crew. Delay was claimed as... Yes.... ATC..... No compensation? Blame ATC, save money.