If a helicopter can’t fly in dense fog, how in hell’s bells is a motorcade supposed to drive in the exact same dense fog?
Aircraft (jets, helicopters, etc.) flying up in the air at hundreds of mph generally require even better visibility than slow-moving street vehicles (buses, automobiles, etc.) do.
Besides being slower, street vehicles have the advantage of driving along (well-marked) roads, with street signs, medians, traffic lights, embankments, guide planks, etc.
It rarely occurs that street vehicles "crash into the ground" due to poor visibility.
Please use your commonsense!
Regards,