ATA currently uses two levels of reserve. Reserve "A" is a two hour call-out, while Reserve "B" is a twelve hour call-out. A reserve line is initially built with twelve days off and the remaing 18 or 19 days as reserve B. However, the company can "upgrade" the reserve B days to reserve A virtually at will, so you can expect to be at your base, or at least two hours from it, most of the time you're on reserve. The days off come in one, two, or three blocks during the month, with a minimum of three days per block. So you could have three blocks consisting of 3, 4, and 5 days off or one block of 12 days off or something in between.
If you are on one of the airplanes that operate scheduled service (i.e. the 737 and 757 in MDW and IND) you'll get a nine hour "rest period" during each of your reserve days. This is assigned at the whim of the schedulers, thus your rest period could be three in the afternoon to midnight. If you're fortunate to fly the TriStar, you'll be on call 24 hours a day, as all the L1011 flying is "supplemental", and not subject to FAA scheduleld service rest requirements.
This month I have had 13 out of a possible 19 days of reserve B upgraded to reserve A. However, I have only been called out to fly one four day trip, making this the best part-time job I've ever had. Unfortunately, ATA pays me like it's a part-time job.
Hope this wasn't too confusing. Of course all of this may change in the next contract. Bottom line, is that if you commute to sit reserve, it'll s*ck. I did that for a while. Now I live within two hours of my base and my quality of life is good. Now did I mention the shortcomings of my paycheck?
Congrats on the interview. Get the job and you can experience all of this fun for yourself.
Good luck,
Brad