Have you recently invested in smart luggage with a built-in charger to keep your phone and gadgets fueled up on your journey? These bags are a rapidly growing travel trend and can be a great addition to your on-the-go lifestyle. If your new luggage has built-in lithium batteries, though, buyer beware.

American Airlines recently cracked down on carry-ons with built-in batteries and will now require passengers to prove the batteries can be removed from the luggage before allowing them to fly. Lithium batteries are permitted and safe in the airplane cabin, but potentially dangerous in the plane’s belly — so if your carry-on bag gets checked at the gate unexpectedly, this can pose a problem for the airline.

Your bag will be safe as long as you can prove the battery is removable so, when looking for a bag either for yourself or a loved one, keep this in mind.

American Airlines isn’t the only carrier cracking down on these high-tech bags. United Airlines stated they are working on a similar policy, as are Delta Air Lines and Alaska Airlines.