Almost every delay happens because the aircraft is somewhere else. If it hasn't left its previous city yet, your departure will move - regardless of what the board says. This is how you know before anyone announces it.
Waits differ by 30 minutes or more between checkpoints at the same airport - and you can enter through any of them, whatever airline you're flying.
These are each carrier's own written commitments on the US DOT dashboard. Citing them by name works far better than asking generally.