I’m gonna contribute here; I’ve been getting abysmal performance after a few hours of flying around, and I think I pinned it down to photogrammetry. It’s not just London: areas like Atlanta, Hartford, Fargo, Minneapolis, etc., all eventually cause FPS to tank abysmally low (talking ~5FPS or less) after hours of flying.
I’m not sure what the deal is; is it that photogrammetry gets loaded into the session and never unloaded after you leave the area?