Frontier Airlines is based in Terminal 1 at San Francisco International Airport (SFO). Terminal 1, also known as Frontier Airlines SFO Terminal the Harvey Milk Terminal, is a new facility with plenty of amenities such as restaurants, retail stores, and seating areas. Frontier Airlines passengers can check in at designated counters or at self-service kiosks. The terminal is user-friendly, and security lines are quick. Make sure to confirm your gate assignment and get there even earlier as SFO can be pretty hectic during peak travel periods.