@Giana, sitemail sent. Thanks. 

@Lenord, some very interesting places you've been. Yeah, those craft look much more like fighter jets than faking it with odd birds; I think the problem is MidJourney's in-built nanny functions. It probably goes: "city with birds flying over ok, city with airplanes flying over okay, city with jet fighters flying over NOT okay but the rest of the prompt isn't over the line enough to trigger the forbidden warning so better  mess it up a bit just in case".