Metering summer 2022 probably. There's still time to head it off but based on the weak vacancy they either aren't aware of it (hard to imagine) or don't care. Something will have to change. They're blowing through double digit numberrs of junior mans every single day right now just to try to limit the cancellations, which are coming hot and heavy anyway.
I predict they're going to let the operation fall apart somewhat to annoy passengers until congress reverses the 1500 hour rule. All three majors are gearing up for a lobbying effort in that direction.