At least in the morning the airlines have had the overnight to unsnarl the previous day's mess because of the reduced revenue traffic overnight and the corresponding slack that accrues as a happy side effect.
This is also why things like the healthcare system, transportation network, and postal system shouldn't be run for maximum utilization/efficiency under normal load: if there isn't any slack in the system it gets real ugly when things get squirrelly. In cases of localized disturbance, we get by on mutual aid: linemen and bucket trucks from far away respond in the aftermath of e.g. a hurricane or tornado. Likewise, fire departments from all over The greater Boston area responded to the gas explosions in the Merrimack Valley[0] and companies from even further away repositioned trucks to cover the departments that responded directly.
When it's national or global scale event, you're left leaning on whatever slack was in the system. As we're all painfully aware, there hasn't been enough. The public health and healthcare systems have been doing heroic work, but if they weren't stretched so tight in the name of efficiency beforehand, there'd be less need for the heroic efforts.
[0] https://en.wikipedia.org/wiki/Merrimack_Valley_gas_explosion...