Airline Time Changes
Having worked in the travel industry as a travel agent, hopefully this will provide some insight:
Generally, the rule of thumb when I worked as a travel agent was that if the airline changed flight times by more than 15 minutes (earlier or letter), thet were to notify you directly, whether by phone or email of the change. I can't remember if that was a set in stone policy, or more of an industry standard.
If the change was less than 15 minutes, no notification was sent out by the airline. Small changes are quite common; with so many flights in and out of different airports, small shifts in scheduling occur all the time, from the moment you book until you actually take off/land.
What sometimes happens is this: Over the course of a week or two, your flight time will be changes by 10 or 15 minutes each time. So a 12 minute change on Monday, and a 13 minute change on Wendesday, and so on... no notification, because they are all less than 15 minutes. A few weeks of that, and you're off by an hour or more from your original time.
The sad truth is, you have to check on your flights. Often. I check my flights at least once a week, usually every few days.
If a huge change is made, you should be notified. But the responsibility ultimately is that of the passenger. If a major change in scheduling is unacceptable to you, call as soon as you can and try to make changes. The earlier you do, the better chance of getting what you want.
And if you get an agent who is less than helpful, try to be as polite as possible and let them know you will call back shortly. Then hang up and redial, and hopefully you will get someone who is more helpful. Be careful not to get too worked up... the agent types notes into your reservation which travel with it to the next agent... that name calling you just did might come back to haunt you on your next call in.
On a personal note, Delta has changed all of our flights in September. Mostly just a few minutes here or there, but one of the legs moved a total of a half hour later. No notice of course, because it was done in three seperate small time changes.
Crazy, isn't it? Good luck to everyone!