QuantumHED wrote:
So would it be safe to say that a large commercial aircraft flying overhead
at a stupidly low altitude like 20 feet wouldn't be nearly strong enough to
overturn vehicles?

At the local international aiport a road goes past each end of the runway well
below the flightpath. I've never heard of was tipping anything over on these
roads. However there is an embankment at one end which is close to the level of
the runway which when I was young was fun to stand on when the planes came in
or took off overhead. The wash here was significant but fear made people fall
down more then the wind. These days there are signs there warning of the
dangers of jet blast and men come and yell at you if you stand there. I guess
people were injured after being knocked over by the wash or falling down in
fear. The wake of the body of the plane going over was inconsequential compared
to the wash from the engines. I reckon it would be possible to knock over a
high sided vehicle with the engine wash, but it'd need to be sideways under a
large jet taking off.