We went last year the first week in September. I booked our tickets in June and paid $720 for 4 tickets from Pittsburgh. The first week in July all the airlines dropped their fares to $99 RT. I think if you are patient you should be able to get a really good fare for that time. I have checked the last few years and the fares have always been low in September and October. I was worried last year with the rising gas prices, so I booked. I could have saved $200 or more. I flew USAir so of course I couldn't change without a penalty. I am also waiting on Southwest. I have found, though, for Pittsburgh the best fares are only available less than 3 months in advance.