The first link and the last one are either fairly long lenses or big crops from a larger image.
The middle one looks to be about 35mm equivalent. Just guessing on that one.
The math is just trigonometry. You have three basic variables: the lens' angle of view, the distance (range) to the subject and the height of the resulting projection on the ground.
I'd shoot some tests on subjects of known dimensions at known distances to get a feel for what's needed.
I've only shot medium format film from the air, never MFD, but I imagine that any lens over about 150mm is going to be a bit of a handful. Given the ease of enlargement with MFD, in the air you're better off too wide than too tight.
The only way to get a hand-held, near-vertical shot is in a very tight turn. Not as difficult as it sounds, but a little disconcerting the first few times if you have the door off. If you do it a few times in succession, you may barf. Be prepared.
Good luck shooting below 1000 ft in residential areas. 2000 ft is the usual legal minimum in my experience.