Rod Broome, a retired pilot from Minnetonka who spends much of the year traveling, knows that airlines are cracking down on overweight bags, charging from $50 to $100 for one. That's why he never flies without his portable digital luggage scale. Yet Broom sometimes encounters discrepancies between his scale and those at airports.

Kate Hanni, director of a national nonprofit consumer rights group called flyersrights.org, says that such discrepancies are not uncommon. "Baggage has become a billion-dollar business," she said. "It's become a much more prominent issue."

In Minnesota luggage scales are checked on a 12- to 15-month rotation by Weights and Measures at the Minnesota Department of Commerce, but there are no national standards.

Hanni said that with more baggage fee increases on the way, airports need to test scales at least quarterly. She is an advocate for luggage scale testing standards that apply to all airlines.

What if the reading on an airport scale doesn't match your portable scale? If the differences cost you, reweigh your bag on a different scale. Each scale should display a sticker that shows when it was last tested.

Travelers can report inaccurate scales by going to tinyurl.com/travelscales. Be sure to note the location of the luggage kiosk or check-in station. Most travelers are unaware of this recourse since airlines and airports are not required to post the information.