Thank you for calling to let me know when a flight is delayed; that's a really valuable service, especially because I tend to forget to check flight times.
However, it would be a much more valuable service if you were to make such calls more than an hour before the originally scheduled departure time.
Say I check online a couple hours before the flight and confirm that my flight is on time. I go to the airport. I arrive at the terminal an hour before my flight, as you recommend. I look at the departure screen, and discover that the flight has been delayed.
And then I get an automated phone call telling me brightly that my flight has been "updated." Which is to say, delayed.
Wouldn't it have been more helpful to tell me that, oh, an hour earlier?
To be fair, I'm guessing that a lot of the time flights get delayed at the last minute; and if I were running really late, it would be a relief to get that phone call.
Still, I'd appreciate it if you could work on sending notifications earlier whenever possible.
(Today it's Southwest, but I think I've had the same problem with at least two other airlines this summer.)