So the "40 airports" are almost certainly all the Class Bravo airports in the USA, which are all the big ones.

A very good web site every frequent flier should have bookmarked is the FAA National Airspace Status page. https://nasstatus.faa.gov/ It will lay out what's going on, and if you click the "View Full Operations Plan" link 2/3 of the way down, you can see the gritty details on what's going on.