give yourself lots of time if using AT out of PIT
we flew them on 6/26, 6:45 amish flight on a Saturday. I figured we could arrive 2 hours early & breeze thru...not! Even though I had upgraded to business class & was able to use the short line to checkin, the zealous reps were using a measuring tape to check what seemed to be every piece of luggage that looked to be near oversize
several people were really complaining as they missed their fights, did get rebooked no extra cost.
when it was my turn, the same bag that flew 2 other trips on AT magically grew

despite it being lightly packed as i had 2 'free' checked bags pp allowance. I insisted they note my account as i knew the bag was less than 61 inches, forked over $49 & then hustled to our gate, where they had already started to board
as bonus points, my garment bag had the side ripped off it when i collected it from the luggage carousel in FLL & my cruise clothing was a bit beat. They gave me a new piece of luggage on the spot (and instructions to call AT to comlain)...quite curious, they had a whole room full of any size suitcase u could imagine.
i indeed called AT & told them my story, notice the quickie trip @ the end of the month,
booked @ heavy discount upon my return.
good luck OP