$125 Cheap Frontier Airlines flights Denver (DEN) to Islip (ISP)

Apply the “Price (lowest to highest)” filter on Expedia to look for cheap Frontier Airlines return flights from $250 from DEN to ISP. Affordable one-way fares from $125 are available as well.**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.

January is one of the least expensive months to jet off to Islip with Frontier Airlines. You could also find excellent prices on return and one-way fares in February.

To find cheap Frontier Airlines fares from Denver Intl. Airport (DEN) 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 the cost. Sunday is typically the cheapest, while Monday is often the most expensive for domestic flights. You can save 6% on average by booking your flight 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.

Click on our “Nonstop” filter when browsing for direct Frontier Airlines flights from DEN to ISP. It’s also an easy way to compare other airlines offering the same direct trip.

Find Frontier Airlines’s earliest flights from DEN to ISP by selecting the “Early Morning” and “Morning” filters. Not only will you arrive sooner, early departures also have a 20% less chance of being canceled.**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.

MacArthur Airport (ISP) is the main Islip gateway for Frontier Airlines flights from Denver Intl. Airport (DEN).

Journey from DEN to ISP with Frontier Airlines and look forward to a host of benefits starting with a rewarding loyalty program. When you book through Expedia as a Frontier Miles and One Key™ member, you could also earn OneKeyCash™* to use on select future travel purchases.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.

In most cases, you can reschedule or cancel your flight, although there may be additional fees if your booking was made more than 24 hours ago. Need flexible options? Use our “No cancel fee” and “Changes included” filters to find flights that won’t charge you extra if you need to adjust your plans. To modify your booking, visit “Trips,” select your flight and click on “Manage Booking” for more details.