$107 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 1/31. 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
$144
Overall average: $333
Frontier
Thu 2/19Thu 2/26
PHL - DEN • Non-stop
Cheapest non-stop
$164
Typical prices: $249-$449
Frontier
Mon 2/23Thu 2/26
PHL - DEN • Non-stop
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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

Thu, Feb 19 - Thu, Feb 26
Frontier Logo
5:42 pm - 8:12 pm
PHL
-
DEN
4h 30mnonstop
Frontier Logo
6:00 am - 8:12 am
DEN
-
PHL
24h 12m1 stop
$144Frontier
Thu, Feb 19 - Wed, Feb 25
Frontier Logo
5:42 pm - 8:12 pm
PHL
-
DEN
4h 30mnonstop
Frontier Logo
12:59 am - 11:18 am
DEN
-
PHL
8h 19m1 stop
$145Frontier
Wed, Jan 28 - Sat, Jan 31
Frontier Logo
8:00 am - 8:30 am
PHL
-
DEN
26h 30m1 stop
Frontier Logo
6:00 am - 7:13 pm
DEN
-
PHL
11h 13m1 stop
$147Frontier
Tue, Jan 27 - Wed, Jan 28
Frontier Logo
6:00 am - 12:19 pm
PHL
-
DEN
8h 19m1 stop
Frontier Logo
7:30 am - 3:37 pm
DEN
-
PHL
6h 07m1 stop
$148Frontier
Sat, Feb 14 - Sun, Feb 15
Frontier Logo
10:59 pm - 7:55 am
PHL
-
DEN
10h 56m1 stop
Frontier Logo
11:05 am - 4:37 pm
DEN
-
PHL
3h 32mnonstop
$149Frontier
Sun, Jan 25 - Tue, Feb 3
Frontier Logo
8:45 am - 9:49 pm
PHL
-
DEN
15h 04m1 stop
Frontier Logo
6:32 pm - 10:37 am
DEN
-
PHL
14h 05m1 stop
$151Frontier
Tue, Jan 27 - Sun, Feb 1
Frontier Logo
2:58 pm - 9:04 pm
PHL
-
DEN
32h 06m1 stop
Frontier Logo
11:25 am - 11:25 pm
DEN
-
PHL
10h 00m1 stop
$152Frontier
Fri, Feb 13 - Sat, Feb 14
Frontier Logo
7:05 pm - 9:42 pm
PHL
-
DEN
4h 37mnonstop
Frontier Logo
12:01 am - 11:18 am
DEN
-
PHL
9h 17m1 stop
$153Frontier
Mon, Feb 23 - Thu, Feb 26
Frontier Logo
7:53 pm - 2:06 pm
PHL
-
DEN
20h 13m1 stop
Frontier Logo
2:10 pm - 1:01 am
DEN
-
PHL
8h 51m1 stop
$154Frontier
Wed, Feb 4 - Thu, Feb 5
Multiple Airlines Logo
12:40 pm - 8:19 am
PHL
-
DEN
21h 39m2 stops
Multiple Airlines Logo
2:57 pm - 7:59 pm
DEN
-
PHL
27h 02m1 stop
$155Multiple Airlines
Useful Info

Good to know

Low seasonJanuary
Cheapest flight$107
Best time to beat the crowds but there is an average 4% increase in price.
Most popular time to fly and prices are also 13% 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 20m.

  • How many flights are there between Philadelphia and Boulder?

    13 direct flights run between Philadelphia and Boulder on a daily basis. On average, there are about 94 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 Thursdays.

  • 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 $65. Frontier offered a round-trip connection from $106 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 40 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 November, December and January. The cheapest month to fly is July.

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 4249 reviews
8.0Comfort
8.6Crew
8.1Boarding
7.0Food
7.5Entertainment
Airline reviews

The flight crew was extremely rude and especially not helpful when our flight was delayed.

2.0 MediocreMatthew, Jan 2026
DAL - SAN
Read more Southwest reviews

The flight crew was extremely rude and especially not helpful when our flight was delayed.

Pretty seamless, just a tad bit late in taking off and landing.

Flight was fine other than there was a gate change that I was not notified of. By chance I happened to check my phone and saw the change, otherwise, we would have missed our connecting flight.

Haven’t flown on SW in years. Flight was on time departing and arriving. Served vegan butter onion flavored pretzels which were bad. Coke served was in a tiny paper cup. Crew was not engaging. Felt like they were going through the motions. Old plane, tight seats and no leg room.

Check-in, Boarding and flight were smooth. All the employees and crew was very nice and funny. They gave the kids crayons and workbooks to keep them occupied which was a big win. I’ve flown Southwest many times and that’s the first time I’ve seen that and it is a great addition.

Flight was on time. Wi-fi was a little spotty/slow. Boarding and exit were efficient.

Okay, not wonderful. Short flight. Wi-fi didn't work properly. Stuck waiting for a gate to open upon arrival for 20 or so minutes.

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.

Flight was late from Newark to Atlanta, I asked flight attendant to please let my family of 3 out first when we landed to Atlanta because we were late for our connecting flight to Quito. She didn't and we were late for 5 minutes we couldn't board the plane and spend hours trying to get another flight with customer service for the next day.

I really liked the legroom. I am 6’4”.a at For some reason our seats were not together and using the app to fix it didn’t work. Passengers were nice enough to move for us but you should absolutely ensure a parent sits with their child.

Late delayed flight delays boarding and delays leaving and delays on arrival too. Cramped plane no room no food.

DTW line is too long. The flights from DTW to BWI are always delayed for unknown reasons.

Delta canceled our flight and we had to scramble to find another airline to get home. Phoenix is not a delta hub so they didn’t have another plane. It would have been a red eye though Salt Lake City. Getting in at 5am. No bueno.

This flight was no comparison to our prior flight. I'm thinking it all has to do with the age of the aircraft.

This flight was a first class choice and left much to be desired. Seat backs on seats were falling apart and torn. Seats actually didn't come to a "full & upright position". Pull out table was sprung. Not any significant leg room. All in all we were on an obviously older plane and felt overcharged for what we received as first class.

Flight was delayed several times. At one point, they "pulled back" 15 minutes from the delayed boarding and sent a text saying we would board sooner than previously advised. The flight then was delayed again. And when we boarded, there was an unspecified technical issue which had us waiting in the plane for about an hour.

Delta is a good airline. I've never had an issue with Delta. I'll continue to fly with them until they show me that I shouldn't.

The only thing nice I can say is the flight crew was really nice and apologetic about the situation. They shared as much information as they had and advised us on what we could do about missing connecting flights. The boarding process was so slow. The gate agent was working by herself and should have had someone working with her. It took almost an hour to board because she was trying to board a full flight of people and provide customer service to everyone who was flying standby and/or had questions. It was really chaotic. This didn't help the fact that we were delayed and folks were missing connections the longer it took.

The flight was delayed by two de-icings. The seatbelt did not work correctly. It did not stay tight.

Hotter than Hades in August. Why, why do crews think that in the winter when we are already dressed for cold weather we need a cabin that is 82 degrees. Even the vents were blowing hot air.

Flight was delayed. De-icing took a while. When we landed had to wait for another plane to vacate our gate. Just an overall bad experience.

Not good - outbound flight was delayed and missed my connection even though I got to the gate after running through the airport - the agent would not let me on because the door was closed (flight had not left). There was no notification from United - overall experience was very disappointing. Additionally, I was downgraded from first class to coach on the alternative flight

United have really come back. Airport and boarding process is clear and good, app and information also very good

My husband and I recently had an unfortunate experience with Lufthansa. At the Philadelphia International airport, the ground staff refused to board us because we didn’t have a current visa stamped on our passports for Frankfurt. We completely understand that this was our mistake. we should have double-checked the visa requirements before our trip. However, the issue that upset us most was how the situation was handled by the staff. They told us they would mark it as “boarding denied due to visa issue”, but instead they recorded it as “no show”. Because of that incorrect entry, our return flight was automatically cancelled as well, which caused additional stress and expense. Mistakes can happen, but we expected more transparency and accuracy from a reputed airline like Lufthansa. It would have made a big difference if the staff had been more careful and considerate in documenting the situation correctly.

The entertainment available didn’t work for anyone on the flight. Long 6 hr flight with no entertainment option and the staff didn’t know until an hour into the flight when we made sure they knew about it. They had no way to fix it.

Late FA meant slow boarding. WiFi did not work. I’m a medium plus sized passenger. The seatbelt was for the first time ever barely fitting. And we delayed on the tarmac 40 min

My husband and I had boarded the flight from Denver to Chicago, and one of the last passengers to get on the plane opened the overhead bin above my husband's seat and threw his bag out of the bin to make space for his own. He said, "Mine is bigger!" The flight attendant supported the new passenger. They didn't care that my husband has two artificial knees and must have the foot room in front of his seat to be able to fit his legs in -- and to be able to stand, much less walk, at the end of the flight. I have never seen this happen before, and it was a disaster.

Terrible. They wouldn't allow me on my flight on the 14th..

Everything about the flight was lovely. My only suggestion would be to offer a few more options of tv series from Apple TV or HBO.

Delays to take off and to leave the plane after landing added a lot of time to this flight.

The Phildalphia to Allentown portion was a BUS, not a plane. All was as expected.

Excellent - explanations were clear staff was nice and flight was comfortable

Flight was delayed not sure why no explanation given and no apologies either. Otherwise the flight was fine

Did not get the seat I selected and paid for.

Plane was delayed for 6 hours, at first by weather, which is understandable, but was further delayed with NO given reason for 2 1/2 hours more. We had no clue when we were going to depart actually until they opened the ramp. VERY POOR to ZERO COMMUNICATION!!!

Flight was delayed and after being in the airport for like seven hours, it was canceled.

Flight delays numerous times. Everytime we would get close to boarding it would be delayed again. Strung along the entire time.

Overall very good, only complaint I have is the crew from CLT to SAT could have collected trash sooner.

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.

sluggish boarding and arrival procedures, fake nice flight attendants, and lots of delays.

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.

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

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