$118 Find Cheap Flights from Philadelphia to Boulder - Compare and Save

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 7/17. 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
$199
Typical prices: $432-$229
Frontier
Wed 9/2Thu 9/3
PHL - DEN • Non-stop
Cheapest non-stop
$199
Typical prices: $446-$236
Frontier
Wed 9/2Mon 9/7
PHL - DEN • Non-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
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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

Wed, Sep 2 - Thu, Sep 3
Frontier Logo
12:42 pm - 2:56 pm
PHL
-
DEN
4h 14mnonstop
Frontier Logo
6:05 am - 11:47 am
DEN
-
PHL
3h 42mnonstop
$199Frontier
Thu, Aug 27 - Sun, Aug 30
Frontier Logo
12:42 pm - 2:56 pm
PHL
-
DEN
4h 14mnonstop
Frontier Logo
11:59 pm - 5:38 am
DEN
-
PHL
3h 39mnonstop
$200Frontier
Wed, Jul 22 - Sun, Jul 26
Frontier Logo
12:44 pm - 2:58 pm
PHL
-
DEN
4h 14mnonstop
Frontier Logo
6:05 am - 11:49 am
DEN
-
PHL
3h 44mnonstop
$202Frontier
Sat, Aug 22 - Tue, Sep 1
Frontier Logo
12:42 pm - 2:56 pm
PHL
-
DEN
4h 14mnonstop
Frontier Logo
9:06 pm - 7:19 am
DEN
-
PHL
32h 13m
2 stops
$203Frontier
Wed, Aug 26 - Thu, Aug 27
JetBlue Logo
8:28 am - 1:15 pm
PHL
-
DEN
6h 47m
1 stop
JetBlue Logo
11:37 pm - 8:22 am
DEN
-
PHL
6h 45m
1 stop
$204JetBlue
Wed, Jul 29 - Mon, Aug 3
Multiple Airlines Logo
12:44 pm - 2:58 pm
PHL
-
DEN
4h 14mnonstop
Multiple Airlines Logo
11:37 pm - 8:30 am
DEN
-
PHL
6h 53m
1 stop
$205Multiple Airlines
Mon, Aug 10 - Tue, Aug 18
Frontier Logo
12:54 pm - 3:08 pm
PHL
-
DEN
4h 14mnonstop
Frontier Logo
6:30 am - 7:03 pm
DEN
-
PHL
10h 33m
1 stop
$206Frontier
Wed, Aug 19 - Wed, Aug 26
American Airlines Logo
7:30 am - 9:39 am
PHL
-
DEN
4h 09mnonstop
American Airlines Logo
10:29 am - 4:14 pm
DEN
-
PHL
3h 45mnonstop
$207American Airlines
Wed, Aug 5 - Wed, Aug 19
Frontier Logo
12:44 pm - 2:58 pm
PHL
-
DEN
4h 14mnonstop
Frontier Logo
6:05 am - 11:47 am
DEN
-
PHL
3h 42mnonstop
$208Frontier
Tue, Aug 4 - Mon, Aug 17
Multiple Airlines Logo
12:44 pm - 2:58 pm
PHL
-
DEN
4h 14mnonstop
Multiple Airlines Logo
11:37 pm - 8:35 am
DEN
-
PHL
6h 58m
1 stop
$209Multiple Airlines
Useful Info

Good to know

Low seasonJanuary
Cheapest flight$118
Best time to beat the crowds with an average 10% drop in price.
Most popular time to fly and prices are also 15% 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 3h 55m.

  • How many flights are there between Philadelphia and Boulder?

    18 direct flights run between Philadelphia and Boulder on a daily basis. On average, there are about 131 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 Saturdays 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 5 days, the cheapest one-way ticket between Philadelphia and Boulder found on KAYAK was with Frontier for $60. Frontier offered a round-trip connection from $99 and United Airlines from $196.

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 May, June and July. 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.
7.9
SouthwestOverall score based on 4234 reviews
8.1Boarding
8.0Comfort
7.0Food
8.6Crew
7.5Entertainment
Airline reviews

Slow boarding, limited food and drink portions. Bad delays and turbulence

6.0 GoodAnonymous, Jun 2026
MCO - MKE
Read more Southwest reviews

Slow boarding, limited food and drink portions. Bad delays and turbulence

there were two flight attendants that were up front...that were the best! They get KUDOs for making my trip only fantastic. Tell them Jeff said that!

OKay. I sat in the back of the plane and it was really loud between babies and little kids, and adults who.like to talk a lot and loudly most of the flight.

Flight coming out of Buffalo was delayed, so we had to be rescheduled on another flight from Baltimore to Phoenix which means we had a long layover and got home 3.5 hours late. Shuttle to parking stopped at 10pm, so we had to pay for an Uber to the parking lot and got charged an extra day of parking since it was after midnight. Not the best experience. Long day!

Was fine, delayed and feels like southwest is always late

I don't know why flying out of Sarasota requires two plane changes.

The first time I flew in the extra legroom section. It was difficult to notice a difference. I had bad luck with my neighbors. The crew was okay. Southwest has reduced the live TV options.

The flight was smooth. The Southwest experience has degraded overall, but this one was okay.

No gluten free snacks. Seats felt worn or bare bones even though it was a new 737 MAX 8.

One major problem that was very unprofessional and uncalled for. Plane landed and we had to wait 20 minutes to get off the plane since they were waiting for someone to come to the gate to drive the jetway. Southwest couldn't have someone available and waiting for the plane to land? Is there only one person in Hobby airport who knows to drive the jetway? Was he at lunch? In the bar? Uncomfortable and uncalled for!

Read the fine print. This was my flight home. I booked my flight for the quickest way home. Had a carry-on and a personal item. Same as my outbound flight. Apparently I needed to pre-pay extra for my carry-on. When I checked in, I was told that I had to check it. I said I’ll pay for it, and was told that this wasn’t an option anymore. They said I still had to pay $50 to check my carry-on. I told them I’ll pay whatever to just carry it in as intended. I was not allowed, so eventually I paid $50 to check my carry-on under a plane that was half full, with overhead compartments that were even less full. My white carry-on suitcase was practically destroyed getting from Idaho falls to Denver to Orange County. The low price air fair was a bait and switch. Got me to the gate, made me pay extra, then didn’t even allow me to pay for a carry on. Not to mention that I paid the $8 for WiFi that didn’t work. All to get my suitcase destroyed. I don’t think I’m going to even keep my Untied mileage plus membership and card. Apparently, membership does not have its privileges for this one.

I flew from Santa Fe to Denver to catch a flight to London and the transfer of my luggage on arrival at Denver to the London flight worked perfectly. The crew on the ground and on board for the London flight were so friendly and efficient.

It was a short flight so I was expecting too much

Late- that’s what United does best. Missed my connection, rebooked to a flight 17 hours later and had to spend $500 on a hotel. What did I get? A $15 meal voucher. What can you get in an airport for $15. I hate United so much.

It was good overall except from Omaha to Denver when flight a was a repeatedly delayed apparently due to some issue at Denver. Communications could have been handled better. I had to board then deboard with luggage and board again

Booked through Kayak Business, had a seat in middle and towards back due to booking rate, not comfortable.

They told us yesterday APR21st that they were cleaning the plane and we got delayed. After that they said they didn't had any crew for the flight so they cancelled the flight till next day.

The flight crew on this leg of my trip was very friendly and pleasant. Every one of them was humorous, as well as helpful and accommodating. This group was BY FAR the best crew I’ve flown with. They deserve kudos.

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

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

Fine. Nothing to write home about. The plane left on time, and arrived on time.

Flight left early and arrived 30 MINUTES early at the destination. Smooth trip.

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.

The flight was delayed after already taxiing from the gate due to a malfunction. After 3 hours we were told the flight was canceled. The next flight available was Sunday. My daughter and I stayed overnight in the airport due to this issue. I was given a $12 meal voucher. Unacceptable

Whole experience was poor. Delayed 2 hours. Lied about the delays. Was all jet blues fault and tried to blame on air traffic control. Sent out other let trips and wouldn't allow people to switch aircraft.

My bag was not loaded on my flight. it was not communicated to me until i was waiting for my bag at my destination. there was no confirmation of when my bag was arriving and no way to track it.

Nice plane, clean, wifi available and movies. All the flight attendants were courteous.

The gate attendant in Boston had a high raspy voice and spoke much too fast to be understood. Not pleasant.

The flight was delayed for more than 3 hours the flight attendant was so angry, it was my first flight with JetBlue but i don’t think I flight with them again.

Since we started at syr the service, crews, and flights were just excellent

It was fine for what it was. It’s not luxury travel but it was efficient, for the most part. Having my carry-on transferred into luggage however, was unwelcome.

We had better-than-average leg room and I loved the access to shows and movies. During boarding, we could not hear the agent even though we were close to the boarding door, which was kind of scary when we realized that half of the passengers had already boarded. Also, the entertainment was awesome, but I could not hear the movie as well as I would have liked, because my headphones were crappy. It would have been better if I could connect my own ear buds via Bluetooth or if JetBlue provided headphones.

On time, friendly attendants, quick wheelchair assistance and help checking in bags. Also appreciated change in seats, more forward to make it easier for my 97 year old mother to board and exit the plane. Thank you, JetBlue!

There weren't enough employees at check in took awhile to get bags checked. There wasn't a wheel chair for me, I was sent to someone who turns out to work for a different airline, if My flight hadn't been delayed I probably would have missed my flight as it was, by the time I arrived at my gate, they started boarding in about 15 minutes. I don't know who took me to my gate, definitely was not the normal people who take passengers to the gate. I'm guessing she may have been in a management position. I wish I knew her name, she went beyond to help me. With that said everyone was kind, and were doing the best they could. So, I choose to say it was an Adventure, stressful start, but good. In the end went well. The situation was not only difficult for passengers but the employee's.

Frontier scheduled a 40 minute connection in DEN. What they failed to mention was that they “close the doors” 20 mins prior to departure, which means you only have 20 mins. Not enough time. Possibly against DOT regulations. Filing complaint.

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!!!

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