Where does Frontier Fly? Frontier Airlines primarily flies to destinations across the United States, Mexico, and the Caribbean, focusing on a wide range of domestic and short-haul international routes. Domestically, Frontier serves over 100 U.S. cities, connecting major hubs such as Denver, Las Vegas, Orlando, and Atlanta. In addition to these large cities, Frontier also flies to smaller regional airports, offering travelers affordable alternatives to more expensive and congested major airports. Cities like Trenton, New Jersey, and Greensboro, North Carolina, are examples of smaller markets that Frontier serves.