Most checked bags in the U.S. are limited to 50 pounds. Anything heavier than that and you’ll pay extra. First and business class passengers, and those with elite status, may be allowed 70 pounds. When you approach the check-in counter, they’ll weigh your bags, and if your luggage is overweight you’ll be assessed an extra fee.
However it’s not always so simple. There’s an unspoken cat and mouse game between airline employees and passengers.