You'll find that almost all airlines keep staff on call in various places and with various reporting times, because already at very small scale, you'll have som

You'll find that almost all airlines keep staff on call in various places and with various reporting times, because already at very small scale, you'll have some crew not making it to work for whatever reason all the time. Maintaining right sized and right placed operational buffers is an entire sub-category of within airline scheduling software/consultancy. Those buffers will never cover a major disaster of course. They should let you hit your on-time and cancellation targets at smallest possible cost, though.