How much would it have cost to build a tornado proof hangar?
Letting alone the forces of the winds very local to the passing tornado, and the probable debris damage, the tornado passing directly over has such low atmospheric pressure that a "sealed" building tries to explode outward, to equalize the pressure, as counter intuitive as it would seem, leaving doors and windows open may be a better idea. From tornadoes we have had in our area, which were not F5), I have formed the opinion that no above ground building could survive, and an underground one would have to be well underground. For aircraft to survive a tornado, they simply must not be in it.