Here's an odd little study of the sort that often gets a lot of credulous media attention. It asserts that weather is the cause of most flight delays.
Well, weather is the attributed cause. But, duh, we've always had weather. Weather alone doesn't explain why three out of ten flights are delayed -- even as airlines build copious slack into their flight schedules to give that airplane lots and lots more time than it actually needs to try to get there without officially being marked as delayed.
An obsolete F.A.A. flight-control system is the primary reason for mounting delays. And a fix is many years off, even assuming the F.A.A. gets its act together under a new administration in Washington. So ok by me: let's blame the weather, which at least we can see coming.