Why You Might Have to Buy a New, Smaller Carry-On IATA guidelines could shrink bags by 40% from previous rules By Arden Dier, Newser Staff Posted Jun 10, 2015 8:44 AM CDT 33 comments Comments Global airlines have announced a new guideline that recommends shrinking carry-on bags. (AP Photo/Donna McWilliam, File) (Newser) – Your carry-on bag might be getting downsized. In an effort to regulate carry-on sizes internationally, the world’s largest airline group, the International Air Transport Association, has proposed a standard carry-on size of 21.5 inches long by 13.5 inches wide by 7.5 inches deep, report the Los Angeles Times. Unfortunately, that's slightly smaller than the size most American fliers will be used to and 40% smaller than the IATA's previous standard—"the equivalent of four soccer balls' worth less volume," reports Quartz. Delta Air Lines, American Airlines, JetBlue, and United Airlines limit carry-ons to 22 inches by 14 inches by 9 inches—a difference of almost 600 cubic inches—while Southwest allows even larger bags, reports NBC News. The proposed standard size hasn’t been adopted across the board yet—it's only a guideline now—but up to 40 airlines are interested in implementing it. Emirates, Lufthansa, and Qatar airlines have already agreed, according to IATA rep Tom Windmuller. "We are confident that over the next several months we will get a number of major airlines coming on board," he says. "This should bring a degree of standardization to the industry and make it easier for everyone concerned." He adds the size was based on talks with Boeing and Airbus and will ensure all passenger bags can fit in overhead compartments, per AFP. The group is already collaborating with luggage makers to produce bags that meet the exact specifications; they'll include a logo, showing the luggage meets IATA rules, and will be out later this year. "The passenger will know that if he or she buys this bag, they'll be able to take it on board a growing number of airlines, that you don't need to be concerned about the size of the bag," Windmuller says.