galaxy flyer, the problem is that replacing air traffic controllers takes time. Even if you take on licensed controllers from other sources/countries, they have to train and validate on multiple sectors in a completely new environment. That may take up to two years. A type qualified pilot can be hired and fly the line in a much shorter period of time than that.
Ronald Reagan proved that wrong. He fired 11,000 ATC employees. Within days operation was at 80% and a lifetime ban was imposed on all strikers from being rehired.
Little or no problem since ... unlike France where this almost seems to be a seasonal occurrence and collectively probably al lot worse over the years than the "end it all" in 1981 in the US.