(NEW YORK) -- Airlines have come under fire recently for their many fees, including the ones they charge passengers for overweight luggage. But are those fees legitimate?
Reporters from ABC's Good Morning America and ABC News affiliate stations across the country went along with inspectors from the National Institute of Standards and Technology's (NIST) Weights and Measures Division recently, checking the accuracy of airport luggage scales.
The NIST inspectors, along with ABC News' reporters, found inaccuracies that could mean a big difference for travelers.
At the Mesa Gateway airport in Phoenix, Arizona, the inspector, accompanied by a reporter with local ABC affiliate KNXV-TV, tested five scales. Four of the scales did not pass inspection, and two had problems so severe they were closed until they could be fixed. One of the problem scales did not zero out, while the other fluctuated wildly.
The airlines charge stiff penalties for overweight luggage. For each bag weighing just one ounce over 50 pounds, Delta Airlines, for example, charges $90, and American and United Airlines each charge $100. For bags that weigh more than 70 pounds, the fees shoot up even higher.
Of the 144 scales inspected at Los Angeles International Airport (LAX) in the past year, six were out of compliance. Bags weighed on those faulty scales seemed heavier than they actually were -- a discrepancy that costs travelers even more.
Scales fail inspection if they are even one-half of an ounce off the correct reading.
On a later, surprise inspection at LAX, NIST inspectors found no faulty scales, but only about 15 were tested that day.
GMA itself researched inspection data from 10 other airports. Of the 2,615 scales GMA inspected, 5 percent were off.
The biggest offenders were John F. Kennedy International Airport and LaGuardia Airport, both in New York. At JFK, 8 percent of the scales were wrong and, at LaGuardia, 7 percent were incorrect.
In some of the nation's busiest airports, scales were surprisingly accurate. In Atlanta, only two of 264 scales were faulty. At O'Hare International Airport in Chicago, Illinois, just three scales were off. And Dallas had only seven bad scales at its high traffic airport.
Before you start thinking that the airlines are out to get you, it's actually the airports that bear responsibility for servicing and monitoring the scales. And, according to one of the inspectors, broken scales often make bags seem lighter, favoring passengers.
But there is something that passengers can do if they suspect a scale is off.
If a scale reads over or under the zero mark even before a bag is placed on it, ask the ticket agent to hit the reset button. Moving your bags around also often changes the weight on a scale.
Another option is to ask that your bags be weighed on another scale.
Copyright 2011 ABC News Radio