I'm sure that heavy title is to any aircraft that its maximum takeoff weight of 300.000 pounds,but I think that the FAA have lowered that weight a while ago to 250.000 pounds to include the Boeing B-757,Though its weired that the only 757 operators I've heard using the title heavy for their 757 is ATA,and Maxicana airline.but none of the other 757 operators like Northwest,American,united,and others.interesting.