I haven't flown Frontier recently, but based on my experience with Southwest and American, it's not unusual for the computer system a ticket, phone, or gate agent is using to be a bit delayed with information. The agent may be giving you the best information that they have--but that information is not always completely up-to-date. Where possible (especially if you're at the airport and think there might be more recent information), it can help to do a little sleuthing on your own.

Almost anyone who has flown Southwest is familiar with its computer system showing an "on-time" departure at departure time, when the aircraft for that flight has yet to arrive at the airport (and sometimes, has yet to take off from the previous airport).

Similarly, I was connecting on AA through MIA a couple weeks ago and checking out options after a 5-hour delay due to 2 separate mechanical problems (they fixed one, we got on the plane, and then a hydraulic leak appeared, so we went back into the airport while they fixed it). While I was on the phone with an AAgent telling me a particular alternate flight was on-time, I walked over to that flight's gate and saw some unusual activity around the plane indicating a mechanical. So I stayed on my original flight and that other flight subsequently changed planes and was significantly delayed.

I didn't doubt the phone agent was giving me the best information she had--it happened I had a way to get better information. And, of course, as shown by the 2 mx's on the original AA flight, sometimes a plane is delayed more than anticipated. AA thought it was going to be 90 minutes, but it turned out--5 hours.

-Hayden