Realistically, the days of highly paid unionised cabin crew are numbered unless the traveling public is willing to pay higher fares.
Yes and the days of highly paid middle management and outsized bonuses should therefore also be numbered unless the travelling public is willing to pay higher fares.
If HR want to terminate an agreement, terminate all salary contracts, bonus entitlements, option awards etc for managers. Make everyone start from scratch, based on the current 'COVID environment'. When the good times return, and they will, guess who'll be 'winning'. It won't be the suckers on an agreement.