ATA's 752's are heavier. I believe Boeing added cargo/pax capacity to ATA;s 752's by adding a small inserted section. Therefore exceeding that 255,000 lbs. As Brad said, a 752's MTOW is exactly at 255,000 lbs. So they can't designate a 752 as a heavy. If it was 255,001 lbs, then yes. But not in the case of a standard configuration of a 752. If you search Heavy, or 255,000 lbs. You'll see this has been discussed about 5 times in rather lengthy threads.