IIUC they legally can't do that. ATC are federal employees, you can't just have private companies pay off federal workers. (Well, I know Trump's friend is literally doing that for the military so idk, maybe laws are just words these days)
In previous shutdowns, Congress passed temporary funding bills to keep paying certain functions such as ATC for a few weeks while negotiating the budget.
This time, negotiations seem to have entirely stalled.
