U.S. Department of Transportation regulators ordered airlines to stop the practice of holding passengers for hours on grounded airplanes. Under the new rules, airlines will have to get travelers in the air within three hours or let them off the plane. Airlines could face fines of as much as $27,500 per passenger for violations. The new rules also say that airlines must provide adequate food and potable water for passengers within two hours of an aircraft being delayed on the tarmac. Additionally, airlines must maintain "operable lavatories" and provide passengers on delayed aircraft with necessary medical attention. The rules go into effect in about three months, officials said. In a statement Monday, Transportation Secretary Ray LaHood said the rules would "require airlines to live up to their obligation to treat their customers fairly." According to Transportation Department data, from January to June 2009, there were 612 planes delayed on tarmacs for more than three hours. In recent years, lawmakers and passengers" rights advocates have demanded federal action to combat such delays. The new rules apply to U.S. airlines and only to domestic flights. They allow exceptions for safety, security and other reasons linked to specific instructions from air-traffic control officials.