Last week Frontier Airlines announced that in June it will expand service from Lambert-St. Louis International Airport with the addition of new non-stop flights to San Francisco, CA, Portland, OR and Trenton, New Jersey, NJ. Both Portland and Trenton are new nonstop markets from Lambert while the San Francisco service adds additional frequency and seat availability. Frontier also offers service to its hub, Denver, CO; Cabo San Lucas, Cancun, Huatulco, and Puerto Vallarta, Mexico; Punta Cana, Dominican Republic; and Montego Bay, Jamaica.Â