ISP - DEN

$75 Find Cheap Flights from Islip to Denver

This is the cheapest one-way flight price found by a KAYAK user in the last 72 hours by searching for a flight from Islip to Denver departing on 3/4. Fares are subject to change and may not be available on all flights or dates of travel. Click the price to replicate the search for this deal.
1 adult
1 adult, Economy, 0 bags

KAYAK searches hundreds of travel sites at once for deals on flights to Denver

 
These are the airlines KAYAK users have selected most often from within our search results in flight searches from Islip to Denver, as well as popular online travel agencies
These are the airlines KAYAK users have selected most often from within our search results in flight searches from Islip to Denver, as well as popular online travel agencies
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Everything you should know

Cheapest round-trip
$166
Overall average: $361
Frontier
Sat 2/21Tue 2/24
ISP - DEN • 1 stop
Cheapest one-way
$75
Frontier
Wed 3/4
ISP - DEN • 1 stop
When to travel
September
Cheapest • 32% price drop
May
Most popular
Good to know
Good to know
+1
+1
Good to know
Good to know
+1
Start a new search
KAYAK searches 100s of sites at once to find you the best travel deals.
We hope you love your trip to Denver!
Flight Deals
Booking Insights
Flight Deals

Cheap Flights from Islip to Denver (ISP-DEN)

 
Here are some of the best deals found on KAYAK recently from the most popular airlines for round-trip flights from Islip to Denver that are departing in the next months. While these flights were available on KAYAK in the last 72 hours, prices and availability are subject to change and deals may expire.
Discover the best prices for you by selecting your travel dates on KAYAK.

Recent round-trip flight deals from Islip to Denver

Sat, Feb 21 - Tue, Feb 24
Frontier Logo
11:41 am - 10:59 pm
ISP
-
DEN
13h 18m1 stop
Frontier Logo
11:59 pm - 1:13 pm
DEN
-
ISP
11h 14m1 stop
$166Frontier
Thu, Jan 8 - Tue, Jan 13
Frontier Logo
8:40 pm - 8:24 am
ISP
-
DEN
13h 44m1 stop
Frontier Logo
11:30 am - 10:46 pm
DEN
-
ISP
9h 16m1 stop
$183Frontier
Wed, Jan 14 - Wed, Jan 21
Frontier Logo
8:00 am - 8:20 am
ISP
-
DEN
26h 20m1 stop
Frontier Logo
11:20 am - 6:48 pm
DEN
-
ISP
29h 28m1 stop
$204Frontier
Thu, Jan 8 - Sun, Jan 11
Frontier Logo
8:40 pm - 10:59 pm
ISP
-
DEN
28h 19m1 stop
Frontier Logo
11:59 pm - 7:51 pm
DEN
-
ISP
17h 52m1 stop
$218Frontier
Thu, Jan 8 - Thu, Jan 15
Frontier Logo
8:40 pm - 10:59 pm
ISP
-
DEN
28h 19m1 stop
Frontier Logo
4:15 pm - 7:50 pm
DEN
-
ISP
25h 35m1 stop
$221Frontier
Mon, Jan 26 - Wed, Jan 28
Frontier Logo
7:43 pm - 5:36 pm
ISP
-
DEN
23h 53m1 stop
Frontier Logo
6:32 pm - 6:48 pm
DEN
-
ISP
22h 16m1 stop
$234Frontier
Tue, Jan 20 - Fri, Jan 23
Frontier Logo
12:00 pm - 10:00 am
ISP
-
DEN
24h 00m1 stop
Frontier Logo
9:41 am - 8:47 pm
DEN
-
ISP
9h 06m1 stop
$239Frontier
Tue, Jan 6 - Tue, Jan 13
Frontier Logo
12:00 pm - 7:59 pm
ISP
-
DEN
9h 59m1 stop
Frontier Logo
11:30 am - 10:46 pm
DEN
-
ISP
9h 16m1 stop
$247Frontier
Thu, Feb 19 - Mon, Feb 23
Frontier Logo
5:07 pm - 7:59 pm
ISP
-
DEN
28h 52m1 stop
Frontier Logo
5:01 am - 2:39 pm
DEN
-
ISP
7h 38m1 stop
$254Frontier
Tue, Jan 6 - Fri, Jan 9
Frontier Logo
12:55 pm - 5:33 pm
ISP
-
DEN
30h 38m1 stop
Frontier Logo
6:31 pm - 7:08 pm
DEN
-
ISP
22h 37m1 stop
$263Frontier
Booking Insights

KAYAK's insights & trends for Islip to Denver flights

Get data-powered insights and trends into flights from Islip to Denver to help you find the cheapest flights, the best time to fly and much more.

What’s the cheapest day of the week to fly from Islip to Denver?

The average price of all round-trip flights from Islip to Denver clicked on KAYAK for each day over the last 12 months.

Your flight ticket price will generally be cheaper if you fly to Denver on a Wednesday and more expensive on a Friday. On your return trip to Islip, you should consider flying back on a Thursday, and avoid Wednesdays for better deals.

What is the cheapest month to fly from Islip to Denver?

To calculate monthly average prices, KAYAK takes all prices for each month over the last year for round-trip flights from Islip to Denver, removes the top 0.1% to account for outliers, and then takes the median of all values for each month.

The cheapest month for flights from Islip to Denver is September, where tickets cost $336 (return) on average. On the other hand, the most expensive months are December and April, where the average cost of round-trip tickets is $653 and $631 respectively.

Good to know

Low seasonJanuary
Cheapest flight$75
Best time to beat the crowds with an average 6% drop in price.
Most popular time to fly with an average 6% increase in price.
Flight from Islip to Denver

When to book flights from Islip to Denver

Are your dates flexible? Find out the best times to travel from Islip to Denver based on our flight data from the last year. Discover the cheapest month and even day to fly.
Estimated round-trip price
KAYAK looks at all historical flight data for each date to provide a predicted price for one-way trips or round-trips with a duration up to 40 days. While we try to provide actual minimum prices for each date, some prices are predictions and actual prices may differ.

FAQs for booking flights from Islip to Denver

  • What is the cheapest flight from Islip to Denver?

    In the last 3 days, the lowest price for a flight from Islip to Denver was $75 for a one-way ticket and $166 for a round-trip.

  • Do I need a passport to fly between Islip and Denver?

    No

  • Which aircraft models fly most regularly from Islip to Denver?

    We unfortunately don’t have that data for this specific route.

  • Which is the best airline for flights from Islip to Denver, Southwest or Frontier?

    The two airlines most popular with KAYAK users for flights from Islip to Denver are Southwest and Frontier. With an average price for the route of $521 and an overall rating of 7.9, Southwest is the most popular choice. Frontier is also a great choice for the route, with an average price of $260 and an overall rating of 5.8.

  • How does KAYAK find such low prices on flights from Islip to Denver?

    KAYAK is a travel search engine. That means we look across the web to find the best prices we can find for our users. With over 2 billion flight queries processed yearly, we are able to display a variety of prices and options on flights from Islip to Denver.

  • How does KAYAK's flight Price Forecast tool help me choose the right time to buy my flight ticket from Islip to Denver?

    KAYAK’s flight Price Forecast tool uses historical data to determine whether the price for a flight to Denver from Islip is likely to change within 7 days, so travelers know whether to wait or book now.

  • What is the Hacker Fare option on flights from Islip to Denver?

    Hacker Fares allow you to combine one-way tickets in order to save you money over a traditional round-trip ticket. You could then fly to Denver with an airline and back to Islip with another airline. Booking your flights between Islip and DEN can sometimes prove cheaper using this method.

  • What is KAYAK's "flexible dates" feature and why should I care when looking for a flight from Islip to Denver?

    Sometimes travel dates aren't set in stone. If your preferred travel dates have some wiggle room, flexible dates will show you all the options when flying to Denver from Islip up to 3 days before/after your preferred dates. You can then pick the flights that suit you best.

Reviews of the top airlines flying from Islip to Denver

 
See real verified KAYAK customer reviews for airlines flying from Islip to Denver. Airline scores are aggregated from all reviews left by passengers on KAYAK after flying with an airline. KAYAK doesn’t show reviews that are older than 5 years. Learn how KAYAK collects reviews.
Need help choosing which airline to fly with from Islip to Denver? KAYAK airline reviews give an overall score for each airline based on loads of factors, including comfort, boarding, in-flight entertainment and more, to make your decision easier. See airline scores according to verified KAYAK customer reviews.
7.9
SouthwestOverall score based on 4250 reviews
7.0Food
8.0Comfort
8.1Boarding
8.6Crew
7.5Entertainment
Airline reviews

They sent a notice that they were boarding an hour early. We had to leave the club and run to the gate. They said sorry, that came from corporate and was a mistake. They did not have enough seating because the flight before it had not taken off on time. They moved our gate and delayed it for an hour.

2.0 MediocreRobert, Dec 2025
LAS - TPA
Read more Southwest reviews

They sent a notice that they were boarding an hour early. We had to leave the club and run to the gate. They said sorry, that came from corporate and was a mistake. They did not have enough seating because the flight before it had not taken off on time. They moved our gate and delayed it for an hour.

The boarding and seat assignment system no longer works for me, but I know it is being replaced. Otherwise, I am good with the overall experience.

The lead steward kept singing about "San Francisco" and hotel California---more annoying than humorous....needs work. Flight was smooth and on time.

Still a fan of open seating. Flight was on schedule and arrived on time. The 737 MAX is very comfortable.

Airline travel is always too cramped to really be pleasant, but the cabin crew on this flight did a pretty good job of making up for it by putting on some music during boarding and sprinkling a few funny remarks into the safety briefing and announcements, and just generally being friendly and helpful. It definitely reminded me of why I prefer the in-flight experience on Southwest!

No delays and arrived to destination 30 min early. Staff was super friendly.

San Diego airport is brand new, spacious, airy and very smooth checkin at SW baggage drop.

Sacrament staff are always polite and helpful. Airport is easy to maneuver and boarding is straightforward.

Flight was delayed due to plane not passing inspection And one of the crew had to time out and we had to wait for another one A 3 hour delay

Near 4 hour flight with only 1 service. Had to use call button to request water. Internet and power not working until into flight. Internet would stop working during flight.

I knew going into this that Frontier, being a low cost carrier, would be pretty bare bones and charge for most extras but this was made up for by the fact that the airplane was a reasonably new Airbus, every employee was great and best of all, Everett Washington is an amazing airport - thanks Frontier for flying there!!!

Seats were new and comfortable. Staff was fine. Missed my connection due to weather -which wasn’t their fault- but got no help at all. Gate staff sent me to customer service, which was and stayed unstaffed. Sign with QR code directed me to call or chat. Chat was useless. Call was returned after an hour. No itinerary offered by Frontier could get me home in less than 30 hours. Rebooked with another airline and got a partial refund that came to about 10 percent of what I paid to get home.

The experience was good. No frills but I got there safe and sound and on time.

As every law enforcement agency I could imagine surrounded the plane and we didn’t disembark for 2 hours and then had to stick around for another hour to go get our personal belongings after leaving them behind and being bused away from the plane, it was scary and inconvenient. We were given no information as to why this was happening. Lack of communication with passengers was disappointing.

Frontier Airlines was AWFUL. I was an hour early for my flight and the lady refused to check me in. I had to purchase a whole new ticket with a different airline.

Late, terrible communication, horrible planning of passenger seating until the literal last minute. One of the worst flying experiences of my life. Y'all suck

First of all, we never got on the connecting flight to Denver. They delayed our flight for two hours. If we would have gotten on that flight, we would have been stuck in Denver for 13 hours. So we re- routed our flight for a straight through flight to Oklahoma two days later. THEN, they delayed that flight for two hours. After that we were able to finally get on our flight and come home. Frontier Airlines - one of the worst airlines I have ever been on.

Terrible communication with weather delay, lost baggage, near impossible to reach customer service

My tickets got canceled on me by your site and I didn't have a flight. Then you kept sending me emails on the status of q flight I didn't have tickets for.

Flight was late. Missed connecting in Denver. My new flight is more than 24 hours later and I have no room, vouchers, or compensation, and might also be bumped from the one tomorrow.

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

Information on your arrival and departure airports