$173 Cheap Frontier Airlines flights Phoenix (PHX) to Islip (ISP)

Finding cheap one-way Frontier Airlines flights from PHX to ISP from $173 on Expedia couldn't be simpler --- just filter by "Price (lowest to highest)." Alternatively, check out our affordable round-trip fares from $341 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.

For cheap Frontier Airlines fares from Sky Harbor Intl. Airport (PHX) to MacArthur Airport (ISP), start searching one to three months before your intended departure. Securing domestic flights 34 to 86 days in advance could save you 25% compared to booking just 6 to 12 days ahead. The day you book can also affect what you pay. Sunday tends to be the cheapest, while Monday is often the most expensive for domestic flights. You can save 6% on average by booking your journey on a Sunday.**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.

Filter your results by "Early Morning" and "Morning" to find the earliest flights from PHX 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.

With a rewarding loyalty program, Frontier Airlines is a top pick for many passengers heading from PHX to ISP. Plus, as a Frontier Miles and One Key™ member booking through Expedia, you can earn OneKeyCash™* on eligible flights along with your airline miles.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.