Suitcases equipped with USB ports and GPS tracking devices—smart luggage—have increased in popularity.

Unfortunately, they may not be the best present this holiday season, as major U.S. airlines announce bans on smart luggage with non-removable batteries.

On December 1, American Airlines announced all high-tech suitcases must have a removable battery to be allowed on board. Since then, Delta and Alaska have made similar announcements. It is projected United and Southwest will soon follow suit.

The restriction means passengers checking smart luggage are required to remove the lithium-ion batteries. If the bag is being checked, the battery must be removed and carried with the passenger on board.

Why the restriction? Unfortunately, the smart luggage lithium batteries have the potential to overheat and cause a fire. If a fire starts in the belly of the plane, crew members cannot access it to put it out—making flights unsafe.

American, Delta and Alaska will start enforcing smart luggage policies in January 2018.