then shouldn't they factor uncertainty much more hence closing airspace?
Listen, it is easy to laugh now, post fact and point out that it was obvious that airspace should have been closed. If you are so clever and everybody else so dumb you should have been here the day before this shooting and warn everyone. Knowledge about what weapons were in the area (and some could imply be rolled in through the border within hours) was quite sporadic and incomplete, not to mention it was hard to predict someone would be so dumb to shoot up and not even engage in routine warning to traffic in the area.