$84 Find Cheap Flights from Philadelphia to Boulder

This is the cheapest one-way flight price found by a KAYAK user in the last 72 hours by searching for a flight from Philadelphia to Boulder departing on 5/18. 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

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Everything you should know

Cheapest round-trip
$118
Typical prices: $415-$210
Frontier
Fri 5/1Fri 5/8
PHL - DEN • Non-stop
Cheapest one-way
$84
Typical prices: $131-$310
Frontier
Mon 5/18
PHL - DEN • 1 stop
Arrival airport
You can't fly directly to Boulder. It is served by Denver (DEN), located 33.4 miles from Boulder.
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Flight Deals
Useful Info
Flight Deals

Cheap Flights from Philadelphia to Boulder (PHL-DEN)

 
Here are some of the best deals found on KAYAK recently from the most popular airlines for round-trip flights from Philadelphia to Boulder 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 Philadelphia to Boulder

Fri, May 1 - Fri, May 8
Frontier Logo
8:41 pm - 11:09 pm
PHL
-
DEN
4h 28mnonstop
Frontier Logo
11:59 pm - 5:37 am
DEN
-
PHL
3h 38mnonstop
$118Frontier
Sat, May 30 - Thu, Jun 4
Frontier Logo
8:35 pm - 11:04 pm
PHL
-
DEN
4h 29mnonstop
Frontier Logo
9:06 pm - 3:16 pm
DEN
-
PHL
16h 10m
1 stop
$119Frontier
Mon, May 4 - Sat, May 9
Frontier Logo
3:10 pm - 9:44 pm
PHL
-
DEN
8h 34m
1 stop
Frontier Logo
11:59 pm - 5:37 am
DEN
-
PHL
3h 38mnonstop
$120Frontier
Thu, May 7 - Sun, May 10
Frontier Logo
8:35 pm - 11:04 pm
PHL
-
DEN
4h 29mnonstop
Frontier Logo
11:59 pm - 5:37 am
DEN
-
PHL
3h 38mnonstop
$121Frontier
Wed, May 13 - Sun, May 17
Frontier Logo
8:35 pm - 11:04 pm
PHL
-
DEN
4h 29mnonstop
Frontier Logo
7:15 am - 1:06 am
DEN
-
PHL
15h 51m
1 stop
$123Frontier
Thu, May 7 - Sun, May 10
Frontier Logo
8:35 pm - 11:04 pm
PHL
-
DEN
4h 29mnonstop
Frontier Logo
11:59 pm - 5:37 am
DEN
-
PHL
3h 38mnonstop
$124Frontier
Fri, May 29 - Wed, Jun 3
Frontier Logo
8:35 pm - 11:04 pm
PHL
-
DEN
4h 29mnonstop
Frontier Logo
6:00 am - 6:40 pm
DEN
-
PHL
10h 40m
1 stop
$125Frontier
Wed, May 13 - Tue, May 19
Frontier Logo
8:35 pm - 11:04 pm
PHL
-
DEN
4h 29mnonstop
Frontier Logo
11:56 pm - 8:59 am
DEN
-
PHL
7h 03m
1 stop
$126Frontier
Thu, Jun 11 - Tue, Jun 16
Frontier Logo
3:49 pm - 9:08 pm
PHL
-
DEN
7h 19m
1 stop
Frontier Logo
6:05 am - 11:47 am
DEN
-
PHL
3h 42mnonstop
$127Frontier
Thu, May 7 - Sun, May 10
Frontier Logo
8:35 pm - 11:04 pm
PHL
-
DEN
4h 29mnonstop
Frontier Logo
11:59 pm - 5:37 am
DEN
-
PHL
3h 38mnonstop
$128Frontier
Useful Info

Good to know

Low seasonJanuary
Cheapest flight$84
Best time to beat the crowds with an average 3% drop in price.
Most popular time to fly and prices are also 14% lower on average.
Flight from Philadelphia to Denver

When to book flights from Philadelphia to Boulder

Are your dates flexible? Find out the best times to travel from Philadelphia to Boulder based on our flight data from the last year. Discover the cheapest month and even day to fly.
Estimated round-trip price

FAQs for booking flights from Philadelphia to Boulder

  • Which airports will I be using when flying from Philadelphia to Boulder?

    When flying out of Philadelphia you’ll be using Philadelphia. Boulder does not have its own airport so you’ll be flying into nearby Denver Intl airport, which is 33.4 mi away.

  • How long does a flight from Philadelphia to Boulder take?

    Direct flights cover the 1,553 miles separating Philadelphia and Boulder in about 4h 01m.

  • How many flights are there between Philadelphia and Boulder?

    20 direct flights run between Philadelphia and Boulder on a daily basis. On average, there are about 144 departures each week.

  • What’s the cheapest day of the week to fly between Philadelphia and Boulder?

    Consider leaving on a Sunday and avoid Saturdays if you are looking for the best rates. For your return to Philadelphia, you’ll find the best rates on Sundays and the most expensive ones on Mondays.

  • How does KAYAK find such low prices on flights from Philadelphia to Boulder?

    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 Philadelphia to Boulder.

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

    KAYAK’s flight Price Forecast tool uses historical data to determine whether the price for a flight to Boulder from Philadelphia 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 Philadelphia to Boulder?

    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 Boulder with an airline and back to Philadelphia with another airline.

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

    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 Boulder from Philadelphia up to 3 days before/after your preferred dates. You can then pick the flights that suit you best.

  • Which airlines provide the cheapest flights from Philadelphia to Boulder?

    In the last 72 hours, the cheapest one-way ticket between Philadelphia and Boulder found on KAYAK was with Frontier for $63. Frontier offered a round-trip connection from $98 and Allegiant Air from $106.

Top tips for finding cheap flights from Philadelphia to Boulder

  • There is no airport in Boulder. Instead, you’ll be flying into Denver Airport when flying between Philadelphia and Boulder.
  • The cheapest flight from Philadelphia to Boulder was found 28 days before departure, on average.
  • Book at least 1 week before departure in order to get a below-average price.
  • High season is considered to be February, March and April. The cheapest month to fly is August.

Reviews of the top 5 airlines serving Philadelphia to Boulder

 
Need help choosing which airline to fly with from Philadelphia to Boulder? 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.
8.0
SouthwestOverall score based on 4330 reviews
7.0Food
8.0Comfort
8.1Boarding
8.6Crew
7.5Entertainment
Airline reviews

The seat was not comfortable. 1D. My back was sore all night and the next day.

8.0 ExcellentJolene, Apr 2026
LAS - DAL
Read more Southwest reviews

The seat was not comfortable. 1D. My back was sore all night and the next day.

Great flight. I didn't get a drink because I was asleep whole on the flight.

Great flight from Seattle to Phoenix and to Chicago-Midway from Phoenix

The new boarding process was easy and straightforward. Very pleasant.

The flight was okay. The pilots did an amazing job and kept us updated on the flight. The flight attendants were okay. They found time to be chatty with each other rather than focus on the guests. One of the attendants was a little less warm when asking about my bag I had on my lap that I was using during latter part of the mid- flight. Mind you, it was not the departure descent. I’m respectful to each and every attendant, it was the tone in her voice reminding me to place my carryon bag on the floor. I hope to have a better experience next time.

The entire travel day was a disaster from beginning to end. Woke up at two in the morning to make it to San Juan airport in time for a 5:30 am flight to Milwaukee which connected in Baltimore. Massive delays lead to me missing original connection out of Baltimore. Sixteen hours of delays/rebooking/layover time later, arrived in Milwaukee to find that only one of two checked bags made it there (despite the fact that Southwest brought another 737 jet to San Juan to fly us out to our original Baltimore connection—-not squeezed into another booked flight). The flight from Baltimore to Milwaukee was barely half full, so there was no logical reason to ship my bags out of Baltimore on a different flight to Chicago to then ship to Milwaukee. Southwest decided that my bags should not have been on the same connecting flight I WAS ON to Milwaukee, and then proceeded to accidentally leave my larger bag with the important items in Chicago. Terrible logic and support all around. Extremely angered and disappointed with SW. What a clownish operation your company has become!

It was as expected and I was grateful for the wheel chair help and ease of use.

One of the best airlines for fast boarding, on time arrivals, and top notch service!

The new seat assignment thing is wierd. If you don’t pay for a seat they always assign you a middle seat regardless of how many people are on the flight. Idk… the new company that bought Southwest is trying to make it more profitable, but I’m just not seeing it. The flight attendants aren’t having as much fun anymore. It just feels like the airline is slowly dying. IMO. We shall see if Southwest is the next Toy’s R Us.

Terrible. Even though there’s assigned seating now, they are still the slowest boarding airline of anyone.

Very old plane with no inflight entertainment. I purchased the internet pass and it was nearly unusable.

My tray was broken so i had no place to work or eat except my lap. Flight attendant said I would get an email with some credit or miles, it was a complete waste of time as I could only function at about 20% of normal. I have not received anything yet.

Short trip, no food and therefore no expectation for much interaction with staff who were pleasant and professional. My critique is on comfort of the seats. Exit rows and comfort seats do not provide enough personal space for 3 side-by-side seats, especially when in the middle row. Some passengers are not considerate of the middle seat and there should be signs that state something to the effect of: "please consider giving middle seats use of the armrests."

My flight yesterday evening was delayed 3.5 hours with no water or food service. Poor experience

Transparency from pilots, quick boarding and exiting the plane, staff greeted to each and everyone,

Didn't like sitting on the waiting pad for 30 minutes right after departing the gate. If you're going to do that, just don't board so people can still get up and walk around in the terminal. My luggage was damaged by the baggage handlers.

Pilots lied about waiting on “paperwork”. Sat in the plane for over an hour, waiting on some papers to be printed according to the pilot and then all of a sudden he says good news maintenance is finally on their way. Maybe they can fix it before we get our paperwork. Ended up missing my connection in LaGuardia and as a result, had a fly home to Lexington instead of the Louisville airport. Then paid $100 to uber to Louisville since it was midnight by the time I got in. I wish they would just be transparent with passengers sometimes and not try to beat around the bush on why things are delayed.

The WiFi was horrific. I fly delta often and love their (usually reliable and free) WiFi. On this flight it was intermittent and when it did connect was extremely slow. I couldn’t get any work done while I was on the flight which was extremely frustrating. I was also in the exit row seat where there is now immediate seat in front of you, so while the leg room was nice, I couldn’t even watch the TV when the internet wasn’t working. Finally, for the last 20 mins of the flight, the announcement indicator came on the TV screens and took them over, even though no announcement was being made. Really disappointed.

The flight was way too HOT! And the plane did not have any in-flight TV entertainment.

The tray table was broken and the food was terrible.

The entertainment options on the seat back video boards were nice.

newer aircraft, ability to connect my headset via blue tooth for entertainment.

The boarding process was straightforward. One pertinent observation regarding all boarding procedures is that if an individual requires assistance or possesses a special status and is part of preboarding, it is advisable to limit the number of passengers who can preboard with them, rather than the entire, sometimes large, companion groups. The seats are uncomfortable, and the entertainment options are significantly inferior compared to other airlines. During the snack service, I requested an additional bag of snacks, but my request was denied. Initially, the flight attendant agreed to my request.becoming a strange accurate moment. The flight duration was four hours.

I had a cancelled flight because of technical issues going to my destination, and a delayed flight coming home. All told it wasn’t a total bust.

During landing. 2 crew members passed 3 times by my lane and didn't notice that people in front of us had their site to the furthermore reclined... That was uncomfortable and could have been dangerous.

Seats are uncomfortable. This has been a trend in the industry for decades. Trying to fit more seats on each plane to increase profits at the expense of the passenger.

It’s always a great time flying with united airlines.

We got delayed three hours and nobody thought to have the bathroom fixed while we were sitting waiting to board? took a full hour to have maintenance come and check it off. Had to shut the bathroom down twice so that the pilots could go to the bathroom. Everyone missed their connections.

Women boarding passengers at the gate was absolutely rude and disrespectful of passengers. The flight attendant was absolutely delightful! Smiling and connected with the passengers. So happy. The seats are cramped and uncomfortable but I guess that’s just the way it is Communication regarding flight was excellent

As great a red-eye flight as red-eye flights can be.

Flight was 3 hours delayed. They gave our plan to two other routes. Need to knock that off.

The flight was on time and the landing was very smooth. The crew and flight attendants were all very friendly and professional.

Plane was super cold. No entertainment unless you were with mileage program Getting off the plane was super slow

I appreciate that I finally got the seat I paid extra for this time. Thank you

Half of the TSA checkpoints at PHL are closed. Also, there is no standby for first class passengers. You can only standby for coach. Very dated policy and inconsistent with peers.

It would have been nice if American tried to care.

Delayed initially because they couldn’t print the flight details. Poor instruction on delay. When I got on the plane the flight attendant argued with me about whether my carry on would fit (it did, although she didn’t acknowledge that). No greeting (other than arguing with me) getting on or off the plane.

Beverage service was not good. Also just one service in 5 hr 30 min flight. No ask fir water ir anything beside one time beverage service.

They are always late and seats was also not having working charger

This flight captain and crew were amazing, started ahead of time of departure and reached 30 mins before arrival time. Amazing!

It was an early flight and most people napped/slept and the crew let us which was nice.

More inflight connection. And leg space is horrible. And the paying for baggage I'd ridiculous!!!

First of all we hade waited 3 hours in the airplane waiting to leave. Second the return schedule was changed and it messed up my entire vaction. I won't buy never again another flight and recommend to nobody traveling with them.

I am writing to express my disappointment with my recent Frontier Airlines flight. I was charged $99 at the gate because my bag was said to be too large, yet once onboard there was no available overhead bin space, and I was required to place the bag under the seat in front of me anyway. This made the charge feel unnecessary and unfair. Additionally, before the flight even took off, I was asked to move from the seat I paid for into a middle seat so another passenger and her cat could have my seat to themselves. I was not offered compensation or an explanation for being moved from a paid seat. Between the unexpected bag fee and being forced to give up my seat, this experience fell well below acceptable customer service standards. I would appreciate a review of this situation and appropriate compensation.

It was costly and difficult to check in. $85 to take a small suitcase with me, carry on or checked and $75 on the return trip, Plus $25 if I didn't check my self in check in $25, because I couldn't do it on the kiosk. Small very uncomfortable seats, waited on the runway for near an hour each way. It was my worst flight to date.

Due to weather, my flight was delayed, further delayed, then canceled. I eventually got through to a support person who helped me find a different route out of MSP, but to get to DIA, they didn't want to, but eventually did help with the connection ticket purchase. But even this replacement flight was delayed time and time again, and I would have missed my connecting flights and I didn't want to get stuck in a layover city, so after 12 hours at the airport with two young boys who were very tired, we just cancelled our plans and spent the week at home, instead of Nana's.

Terrible. Flight cancelled with no reasoning and no flights to rebook. Employees were useless and did nothing to help. Did not even know where to retrieve luggage from the cancelled flight. Flyers beware.

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.

Everything you need to know for your flight from Philadelphia to Boulder

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