The latest dispute stemming from metro Denver’s runaway population growth is heating up this month in Lone Tree, where ambitious plans to double the size of the city are bumping up against concerns about its proximity to a nearby airport. The Federal Aviation Administration recently expressed concern about the RidgeGate East development, which calls for up to 12,000 homes and 9 million square feet of commercial space on 2,200 acres south of Centennial Airport — an area that is under the path of 500 aircraft taking off and landing every day. On Feb.