The U.S. Department of Transportation is proposing a new rule that would ban airlines from charging parents more to sit with their young children.

Under the proposal, released Thursday, U.S. and foreign carriers would be required to seat children 13 or younger next to their parent or accompanying adult for free.

If adjacent seats aren’t available when a parent books a flight, airlines would be required to let families choose between a full refund, or waiting to see if a seat opens up. If seats don’t become available before other passengers begin boarding, airlines must give families the option to rebook for free on the next flight with available adjacent seating.