I wouldn't call the F16 critical. They might even never have been used for an actual mission within Belgium. That nuclear plant though, that is something else. Perhaps also not critical from a 'need this or no more electricity' point of view, but safety-wise this a couple of magnitudes worse than an F16. Word on the street, apparently originating from people working there, is that it has something to do with Engie/France showing off they can do whatever they want.