Santa has to visit ~2 billion kids (assuming 2.5 children per household),
= ~800 million stops on Xmas eve.
Assuming they are equally spread across the planet, each house occupies 0.069 square miles,
which means the distance between each is 0.26 miles.
He has 48 hours on Xmas eve if he travels across the
international date line in the direction of the Earth's rotation.
He has 2/10,000 of a second per household.
He must therefore travel at 1,279 miles / sec. which = Mach 6,395.