It has happened before, so it can happen again:

> On August 5 [1981], following the PATCO workers' refusal to return to work, the Reagan administration fired the 11,345 striking air traffic controllers who had ignored the order, and banned them from federal service for life. In the wake of the strike and mass firings, the FAA was faced with the difficult task of hiring and training enough controllers to replace those that had been fired. Under normal conditions, it took three years to train new controllers. Until replacements could be trained, the vacant positions were temporarily filled with a mix of non-participating controllers, supervisors, staff personnel, some non-rated personnel, military controllers, and controllers transferred temporarily from other facilities. (https://en.wikipedia.org/wiki/Professional_Air_Traffic_Contr...)

At least the Wikipedia article doesn't mention anything about cutting flights...

My understanding is that ATC performance took a nosedive for decades after that. It's possible people died because Reagan wanted to crush a union.

> By prioritizing and cutting flights severely (about 7,000), and even adopting methods of air traffic management that PATCO had previously lobbied for, the government was initially able to have 50% of flights available

It does a bit further down.