Frontier Airlines is adding flights between Des Moines and San Francisco -- a link that airport officials had long sought. Frontier recently began trips to Orlando, too. The company is offering introductory fares. “San Francisco is a growing destination from Des Moines, and this new nonstop service will provide greater travel choices for passengers flying to or from Des Moines,” said Kevin Foley, executive director and general manager of Des Moines International Airport. The San Francisco flights will be Tuesday, Thursday and Sunday with San Francisco arrivals at 10:49 p.m. and return flights to Des Moines landing at 11:55 a.m.