More than 5k flights canceled on Christmas weekend

I don't know the answer to your question, but I do know that there are people whose full-time job is dealing with the fallout of cancellations and over-booking. From my conversations with one of them I'd hazard a guess that it's more or less ad hoc and there isn't any kind of cleverly computed priority algorithm.

I’m not sure there is much in the way of data driving the situation. It largely depends on the root cause obviously but when they get into staffing situations like this, the calculation is nearly impossible. They can reroute crews to more critical flights but that causes such large cascading effects that it’s often best to avoid that if the cascading effects get too complex to solve cleanly and quickly by a person at a work station. I could be wrong though. That’s just my observation from being a frontline employee.

The easiest way to fix these things is throw money at the crews sitting at home on their time off. If that doesn’t work, have more crews available… meaning, hire.

Not a direct/informed answer but a quick look suggests: 5k more than pre-April 2020 cancellations. https://www.vox.com/the-goods/2020/4/20/21224080/coronavirus...