$228 Cheap Frontier Airlines flights San Francisco (SFO) to Islip (ISP)

Finding cheap one-way Frontier Airlines flights from SFO to ISP from $228 on Expedia is simple — just filter by "Price (lowest to highest)." Or check out our affordable return fares from $318 for your next exciting adventure.**These prices were available on Expedia within the past 7 days, for flights departing within the next year. Prices and availability are subject to change. Additional terms apply.

Start searching one to three months ahead of your departure date to score cheap fares on Frontier Airlines flights from San Francisco Intl. Airport (SFO) to MacArthur Airport (ISP). You can save 25% by booking your domestic flight 34 to 86 days in advance versus last-minute reservations made 6 to 12 days out. You could also reduce costs by buying your fare on a Sunday, as it's 6% cheaper on average than a Monday, the most expensive day to book.* Get the timing right, and you can enjoy significant savings on domestic trips.*Ideal booking window recommendation is based on average round-trip ticket prices for January through November for 2024. Best day of the week to book recommendation is based on average round-trip ticket prices for January through October 2024. All data sourced from ARC's global airline sales database.

Sort your results by "Early Morning" and "Morning" to find the earliest flights from SFO to ISP. Heading off early means you're 20% less likely to experience cancellations.**Most reliable time of the day recommendation is based on January through August 2024 flight status data sourced from OAG's global flight data platform.

A rewarding loyalty program and the ability to rack up points through Frontier Miles are the start of the reasons to depart from SFO to ISP with Frontier Airlines. Plus, when you sign up to Expedia's free One Key™ program, you can earn OneKeyCash™* alongside any airline loyalty program earnings. It's yours to spend on your next adventure.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.