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$100+ Cheap flights from Islip to Denver (ISP - DEN)

This is the cheapest one-way flight price found by a Cheapflights user in the last 72 hours by searching for a flight departing on 10/6. Fares are subject to change and may not be available on all flights or dates of travel.
ISP — DEN
Oct 11 — Oct 181
Sat 10/11
Sat 10/18
1 adult, Economy
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Cheap flight deals from Islip to Denver

Discover tips and strategies to find the most affordable flight options for your journey from Islip (ISP) to Denver (DEN). Learn about various techniques such as flexible date searches, comparing prices across and setting up price alerts. Use these methods to find the cheapest flights available for your travel needs. Data last updated September 11, 2025.

Round-trip from

$169
(Priceline)

One-way from

$100
(Cheapflightsfares)

Popular in

April

Cheapest in

February

Average price

$374
From Islip Long Island to Denver Intl
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One-way flight from Islip Long Island to Denver Intl
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Highest demand for flights based on searches. 19% potential increase in price ($115 potential increase over avg. RT price).
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Cheapest flight prices on average. 3% potential price decrease ($15 potential savings vs. average RT price).
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Average for round-trip flights in September 2025
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Find flight deals from Islip to Denver

Cheapest flights from Islip to Denver
Explore the most affordable flight options available from Islip to Denver. Find the lowest fares from popular airlines and budget airlines, with prices last updated on September 11, 2025.

This Priceline deal was found by Cheapflights users on 9/11. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Priceline is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 9/289:49 amISP - DEN
1 stop12h 15mFrontier
Fri 10/312:04 amDEN - ISP
1 stop8h 51mFrontier
Deal found 9/11$169
This Cheapflightsfares deal was found by Cheapflights users on 9/10. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 9/295:05 pmISP - DEN
1 stop8h 08mFrontier
Sat 10/411:59 pmDEN - ISP
1 stop7h 05mFrontier
Deal found 9/10$177
This Booking.com deal was found by Cheapflights users on 9/8. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 11/1111:30 amISP - DEN
1 stop26h 37mFrontier
Thu 11/1311:59 pmDEN - ISP
1 stop6h 55mFrontier
Deal found 9/8$190
This Priceline deal was found by Cheapflights users on 9/8. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Priceline is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 10/65:05 pmISP - DEN
1 stop8h 08mFrontier
Mon 10/1311:59 pmDEN - ISP
1 stop7h 45mFrontier
Deal found 9/8$192
This CheapOair deal was found by Cheapflights users on 9/8. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 10/45:18 pmISP - DEN
1 stop17h 18mFrontier
Tue 10/712:36 amDEN - ISP
1 stop8h 21mFrontier
Deal found 9/8$197
This Cheapflightsfares deal was found by Cheapflights users on 9/10. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 11/34:58 pmISP - DEN
1 stop8h 18mFrontier
Thu 11/611:59 pmDEN - ISP
1 stop6h 55mFrontier
Deal found 9/10$204
This Frontier deal was found by Cheapflights users on 9/11. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 9/295:05 pmISP - DEN
1 stop8h 08mFrontier
Thu 10/22:05 pmDEN - ISP
2 stops18h 35mFrontier
Deal found 9/11$205
This Cheapflightsfares deal was found by Cheapflights users on 9/10. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 10/35:05 pmISP - DEN
1 stop8h 08mFrontier
Wed 10/811:59 pmDEN - ISP
1 stop7h 05mFrontier
Deal found 9/10$206
This Frontier deal was found by Cheapflights users on 9/11. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 10/62:32 pmISP - DEN
2 stops20h 31mFrontier
Sat 10/1111:59 pmDEN - ISP
1 stop7h 00mFrontier
Deal found 9/11$208
This Cheapflightsfares deal was found by Cheapflights users on 9/10. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 10/224:58 pmISP - DEN
1 stop8h 18mFrontier
Sat 10/2511:59 pmDEN - ISP
1 stop7h 08mFrontier
Deal found 9/10$209
This CheapOair deal was found by Cheapflights users on 9/10. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 10/249:49 amISP - DEN
1 stop25h 29mFrontier
Fri 10/3111:59 pmDEN - ISP
1 stop8h 56mFrontier
Deal found 9/10$212

Cheapflights Fare Finder

 
Customize your flight search to find flights from Islip to Denver that fit within your specific budget. Explore options based on user searches and filter the results based on your desired price range. Find flights that match your budget for a cost-effective journey. Over the last 7 days, Cheapflights users made 2,558,603 searches. Data last updated September 11, 2025.
Use the filters below to find and compare flights from Islip to Denver that are best for you.

Fly from

Islip

Fly to

Denver

Route

Depart

Return

Price

IslipDenver

ISP - DEN

ISPDEN

Islip Long Island

Fri 10/3

5:05 pm-11:13 pm

1 stop8h 08m

Denver Intl

Sat 10/11

11:59 pm-8:59 am

1 stop7h 00m

$177

IslipDenver

ISP - DEN

ISPDEN

Islip Long Island

Mon 10/6

5:05 pm-11:13 pm

1 stop8h 08m

Denver Intl

Sat 10/11

11:59 pm-8:59 am

1 stop7h 00m

$177

IslipDenver

ISP - DEN

ISPDEN

Islip Long Island

Mon 10/27

4:58 pm-11:16 pm

1 stop8h 18m

Denver Intl

Thu 10/30

11:59 pm-9:09 am

1 stop7h 10m

$177

IslipDenver

ISP - DEN

ISPDEN

Islip Long Island

Sat 9/27

5:05 pm-11:13 pm

1 stop8h 08m

Denver Intl

Sat 10/4

11:59 pm-9:04 am

1 stop7h 05m

$177

IslipDenver

ISP - DEN

ISPDEN

Islip Long Island

Sat 10/4

5:18 pm-8:36 am

1 stop17h 18m

Denver Intl

Tue 10/7

12:36 am-10:57 am

1 stop8h 21m

$197

IslipDenver

ISP - DEN

ISPDEN

Islip Long Island

Mon 9/29

5:05 pm-11:13 pm

1 stop8h 08m

Denver Intl

Thu 10/2

2:05 pm-10:40 am

2 stops18h 35m

$205

IslipDenver

ISP - DEN

ISPDEN

Islip Long Island

Mon 10/6

5:05 pm-11:13 pm

1 stop8h 08m

Denver Intl

Wed 10/8

11:59 pm-9:04 am

1 stop7h 05m

$206

IslipDenver

ISP - DEN

ISPDEN

Islip Long Island

Wed 10/29

4:58 pm-11:16 pm

1 stop8h 18m

Denver Intl

Sun 11/2

11:59 pm-9:09 am

1 stop7h 10m

$217

IslipDenver

ISP - DEN

ISPDEN

Islip Long Island

Sat 10/11

4:58 pm-11:16 pm

1 stop8h 18m

Denver Intl

Sat 10/18

11:59 pm-8:59 am

1 stop7h 00m

$217

IslipDenver

ISP - DEN

ISPDEN

Islip Long Island

Thu 10/16

9:37 pm-8:15 am

1 stop12h 38m

Denver Intl

Mon 10/20

11:59 pm-9:44 am

1 stop7h 45m

$226

Flights are sorted by cheapest round-trip flights first.

Deals found on 9/8

Showing 1-10 of 19 results
1
2

Best time to book a flight from Islip to Denver

Have a flexible travel schedule? Discover the best time to fly to Denver from Islip with our price prediction graph.
Estimated round-trip price
Rates are based on past data. Find the cheapest month and day to book your flight based on your travel requirements, then search for cheap deals.

Cheapflights Insights

Everything you need to know about your flight from Islip to Denver

What is the cheapest month to book a flight from Islip to Denver?

Currently, October is the cheapest month in which you can book a flight from Islip to Denver (average of $197). Flying from Islip to Denver in March is currently the most expensive (average of $278). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

What is the cheapest time of day to fly from ISP to DEN?

Find hourly flight availability from Islip to Denver. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated September 11, 2025.

It’s typically best to fly out from Islip to Denver in the afternoon. Doing so could potentially save you 45% on the flight price compared to flying at noon, which is usually more expensive.

Reviews of airlines servicing Denver

Get insights into the airlines that provide service to Denver. Read reviews, discover amenities, and learn about the overall travel experience offered by airlines. Use this information to make informed decisions when choosing an airline for your flight to Denver. Reviews last updated September 11, 2025.
Peruse reviews from past customers who have flown with Southwest and Frontier from Islip to Denver to help guide your decision. Users have also rated airlines in terms of entertainment options, comfort, food, crew/service, and boarding process.
Southwest
8.0
Very good
4,248 reviews

Boarding

8.1

Entertainment

7.5

Comfort

8.0

Food

7.0

Crew

8.6

Overall

8.0

Reviews

1 / 20
2.0
Mediocre

Mike,Aug 2025

OKC - AUS

AC was not adequate, even on a night flight. WiFi subpar even for the airlines
Southwest
8.0
Very good
4,248 reviews
Southwest
8.0
Very good
4,248 reviews

Boarding

8.1

Entertainment

7.5

Comfort

8.0

Food

7.0

Crew

8.6

Overall

8.0

Reviews

1 / 20
2.0
Mediocre

Mike,Aug 2025

OKC - AUS

AC was not adequate, even on a night flight. WiFi subpar even for the airlines
Frontier
5.8
Fair
3,177 reviews
Southwest
8.0
Very good
4,248 reviews

Boarding

8.1

Entertainment

7.5

Comfort

8.0

Food

7.0

Crew

8.6

Overall

8.0

Reviews

1 / 20
2.0
Mediocre

Mike,Aug 2025

OKC - AUS

AC was not adequate, even on a night flight. WiFi subpar even for the airlines

Related info for your journey

Find useful and relevant information for your journey from Islip to Denver. Access travel guides, tips, and recommendations to enhance your travel experience. Get information about local attractions, weather, transportation options, and more.

  • How long is the flight from Islip to Denver?

    Departing from Islip to Denver will take you 8h 08m. Airlines will cover a distance of 1654 mi.

  • What are the cheapest airlines flying from Islip to Denver round-trip?

    Flying on Frontier is currently your cheapest option to Denver, with prices starting at $148. Another option worth looking into is Southwest, starting at $377 round trip. Users have found that Frontier is 68% cheaper than the other options available to this destination.

  • Can I find deals for flights from Islip to Denver that include hotel bookings?

    Yes. In addition to deals on Islip to Denver flights, Cheapflights offers vacation packages that include both flights and hotel.

  • How can I find direct flights from Islip to Denver?

    After entering your origin and destination, apply the non-stop filter on the search result page to find direct flights from Islip to Denver.

  • Can I find deals for business class flights from Islip to Denver?

    Yes. Cheapflights offers flight deals from Islip to Denver by cabin class. In addition to browsing deals, you can also filter by cabin class on the search results page after making a search.

  • What is the cheapest month to book a flight from Islip to Denver?

    Currently, October is the cheapest month in which you can book a flight from Islip to Denver (average of $197). Flying from Islip to Denver in March is currently the most expensive (average of $278). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

See more FAQs

Traveling to a place near Denver?

Book flights to Denver if you plan to visit one of these locations
Westminster
Black Hawk
Golden
Winter Park
Broomfield
Greeley
Lone Tree
Lakewood
Cripple Creek
Thornton
Silverthorne
Frisco
Manitou Springs
Fort Morgan
Glendale
Wheat Ridge
Brighton
Longmont
Idaho Springs
Parker

Browse thousands of different options on Cheapflights for your next trip

Toggle through the tabs below to find thousands of options on Cheapflights for your next trip.

Alternative routes for Islip to Denver

See prices for flight routes from nearby airports that may be better suited for you.
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Top 2 airlines flying from Islip to Denver

Discover the top 2 airlines that operate flights from Islip to Denver. Compare their services, reliability, and customer satisfaction ratings to choose the airline that best suits your travel preferences and needs. Over the last 7 days, Cheapflights users made 2,558,603 searches. Data last updated September 11, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$148Average$260FlexibilityNo cancel feeOn-time62%
SouthwestCheapest$377Average$521FlexibilityNo cancel feeOn-time63%

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