US Airways charges an oversize baggage fee for any checked bag with an overall outside dimension between 62 inches and 126 inches as of 2015. Bags larger than 126 inches are not allowed as checked baggage.
US Airways charges a fee for all bags, even those under 62 inches. The oversized bags incur a higher fee than the normal baggage charge. US Airways measures the dimensions by adding the exterior length, width and height of the bag.
Even if the bag is under 62 inches, an additional overweight fee is possible. US Airways charges extra for any piece of luggage weighing more than 50 pounds, with one fee for bags from 51 to 70 pounds and a higher fee for bags between 71 and 100 pounds.