If you think that 6-8 chartered aircraft flying identical routes, at identical times, with identical flight numbers to Monarch aren't related to ZB then you're a fool.
I just had a quick look and found:
TFS-MAN ZB563 13:00
TFS-MAN UA2284 13:00
LPA-BHX ZB425 20:10
LPA-BHX UA2283 19:40
So where are the "identical flight numbers"?
Monarch flew yesterday's flights, United didn't. So I think that for whatever reasons, what may have been a prudent move by the CAA, this and other forums, plus so-called social media have turned it all into a "sky is falling in" moment. Good luck to Monarch.