The head of the Federal Aviation Administration says America's airports are nearing "aviation gridlock" and one day flying may have to be rationed. FAA chief T. Allan McArtor said major cities already are having difficulty coping with the flow of air travel because of a lack of airports and runways. "We already find that weather can bring us to the brink of gridlock," McArtor said in a telephone interview Sunday. "And unless we act, and act soon, we will face a commercial aviation gridlock." McArtor predicted that in a few years the United States will see "planes in one city unable to leave because they can not land in their destination city. Other planes won't be able to fly into the first city because these planes are still on the ground."