The FAA is warning that Delta Air Lines' proposed new lease with Atlanta Hartsfield-Jackson International Airport could be anti-competitive. Regulators are concerned by a clause that gives Delta the right to approve major airport projects, possibly blocking construction that would add more gates and attract new competition. "It appears the lease will limit the city's ability to accommodate a new entrant or existing carrier that wishes to expand at the airport," the FAA noted. But Mayor Shirley Franklin, while admitting the deal is "not perfect," said the city and the airline are building on a model that has worked for many years. "Some people say it's a partnership that will retard development, but Atlanta's experience has been the reverse," she told the City Council, which must approve the lease terms.