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$92+ Cheap flights from Philadelphia (PHL) to Boulder, CO

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 11/16. Fares are subject to change and may not be available on all flights or dates of travel.
PHL — DEN
Oct 14 — Oct 211
Tue 10/14
Tue 10/21
1 adult, Economy
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Cheapflights Tip: The best prices from Philadelphia to Boulder are usually found in August or October, booked 40 days in advance, depart on a Thursday or Friday and return on a Thursday

Cheap flight deals from Philadelphia to Boulder

Keep the following information in mind while searching for Philadelphia to Boulder flight deals. Data was last updated September 14, 2025.

Round-trip from

$171
(CheapOair)

One-way from

$92
(Kiwi.com)

Popular in

December

Cheapest in

August

Average price

$290
From Philadelphia to Boulder
Search Deals
One-way flight from Philadelphia to Boulder
Search Deals
Highest demand for flights based on searches. 6% potential increase in price ($22 potential increase over avg. RT price).
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Cheapest flight prices on average. 1% potential price decrease ($7 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in September 2025
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Find flight deals from Philadelphia to Boulder

Cheapest flights from Philadelphia to Boulder
Explore the most affordable flight options available from Philadelphia to Boulder. Find the lowest fares from popular airlines and budget airlines, with prices last updated on September 14, 2025.

This Frontier deal was found by Cheapflights users on 9/14. 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.
Thu 10/163:59 pmPHL - DEN
1 stop10h 52mFrontier
Tue 10/2111:59 pmDEN - PHL
1 stop8h 35mFrontier
Deal found 9/14$171
This Frontier deal was found by Cheapflights users on 9/13. 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 10/206:42 amPHL - DEN
Nonstop4h 16mFrontier
Tue 10/2112:59 amDEN - PHL
1 stop6h 28mFrontier
Deal found 9/13$172
This Frontier deal was found by Cheapflights users on 9/14. 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.
Wed 10/1511:34 amPHL - DEN
1 stop13h 42mFrontier
Thu 10/1611:59 pmDEN - PHL
1 stop10h 03mFrontier
Deal found 9/14$173
This CheapOair deal was found by Cheapflights users on 9/13. 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.
Thu 10/26:45 amPHL - DEN
Nonstop4h 12mFrontier
Mon 10/611:59 pmDEN - PHL
1 stop8h 35mFrontier
Deal found 9/13$174
This CheapOair deal was found by Cheapflights users on 9/14. 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 10/174:19 pmPHL - DEN
1 stop30h 20mFrontier
Sun 10/1912:59 amDEN - PHL
1 stop22h 00mFrontier
Deal found 9/14$175
This Frontier deal was found by Cheapflights users on 9/14. 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.
Fri 9/2610:16 pmPHL - DEN
1 stop12h 38mFrontier
Wed 10/86:01 amDEN - PHL
1 stop8h 40mFrontier
Deal found 9/14$176
This Cheapflightsfares deal was found by Cheapflights users on 9/13. 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 9/266:45 amPHL - DEN
Nonstop4h 12mFrontier
Fri 9/2612:04 amDEN - PHL
1 stop19h 07mFrontier
Deal found 9/13$177
This United Airlines deal was found by Cheapflights users on 9/14. 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 United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 10/158:00 amPHL - DEN
Nonstop4h 06mUnited Airlines
Sat 10/185:32 pmDEN - PHL
Nonstop3h 37mUnited Airlines
Deal found 9/14$178
This CheapOair deal was found by Cheapflights users on 9/14. 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 9/276:37 pmPHL - DEN
1 stop16h 21mFrontier
Tue 9/304:43 pmDEN - PHL
1 stop19h 07mFrontier
Deal found 9/14$179
This Cheapflightsfares deal was found by Cheapflights users on 9/13. 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.
Thu 10/96:00 amPHL - DEN
1 stop15h 26mFrontier
Mon 10/1312:36 amDEN - PHL
1 stop11h 41mFrontier
Deal found 9/13$180
This CheapOair deal was found by Cheapflights users on 9/14. 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 10/105:30 amPHL - DEN
1 stop29h 48mFrontier
Mon 10/1311:59 pmDEN - PHL
1 stop8h 35mFrontier
Deal found 9/14$181
This CheapOair deal was found by Cheapflights users on 9/13. 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.
Thu 9/257:46 pmPHL - DEN
1 stop25h 39mFrontier
Thu 10/27:15 pmDEN - PHL
Nonstop3h 42mFrontier
Deal found 9/13$182

Cheapflights Fare Finder

 
Customize your flight search to find flights from Philadelphia to Boulder 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 14, 2025.
Use the filters below to find and compare flights from Philadelphia to Boulder that are best for you.

Fly from

Philadelphia

Fly to

Boulder

Route

Depart

Return

Price

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Wed 12/3

5:32 pm-11:04 pm

1 stop7h 32m

Denver Intl

Tue 12/9

11:59 pm-8:36 am

1 stop6h 37m

$245

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Tue 11/18

6:00 am-12:29 pm

1 stop8h 29m

Denver Intl

Wed 12/3

11:59 pm-8:36 am

1 stop6h 37m

$245

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Mon 11/24

7:10 am-2:59 pm

1 stop9h 49m

Denver Intl

Tue 12/2

1:59 pm-11:56 pm

1 stop7h 57m

$257

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Sat 12/6

6:15 am-10:12 am

1 stop5h 57m

Denver Intl

Sat 12/6

3:14 pm-12:35 am

1 stop7h 21m

$257

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Thu 12/4

6:00 am-10:17 am

1 stop6h 17m

Denver Intl

Fri 12/5

12:50 am-10:02 am

1 stop7h 12m

$257

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Mon 12/8

8:00 am-2:09 pm

1 stop8h 09m

Denver Intl

Mon 12/8

6:20 pm-5:50 am

1 stop9h 30m

$257

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Tue 12/2

6:15 am-12:54 pm

1 stop8h 39m

Denver Intl

Wed 12/10

3:14 pm-10:48 pm

1 stop5h 34m

$257

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Wed 12/3

8:05 pm-12:15 am

1 stop6h 10m

Denver Intl

Tue 12/9

5:50 pm-11:22 pm

Nonstop3h 32m

$268

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Sun 10/5

6:50 am-9:00 am

Nonstop4h 10m

Denver Intl

Tue 10/7

5:05 pm-10:30 pm

Nonstop3h 25m

$277

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Fri 10/3

3:45 pm-5:57 pm

Nonstop4h 12m

Denver Intl

Sat 10/4

5:32 pm-11:09 pm

Nonstop3h 37m

$277

Flights are sorted by cheapest round-trip flights first.

Deals found on 9/11

Showing 1-10 of 22 results
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2
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Best time to book a flight from Philadelphia to Boulder

Have a flexible travel schedule? Discover the best time to fly to Boulder from Philadelphia 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 Philadelphia to Boulder

How far ahead should I book a flight from Philadelphia to Boulder?

Use this chart to determine the optimal time to book a round-trip flight from Philadelphia to Boulder. Price data was last updated on September 12, 2025.

Booking 40 days in advance of your planned departure date is, on average, the best time to get cheap flights from Philadelphia to Boulder. The general trend is that the closer you book to the departure date, the more expensive your flight will be.

What is the cheapest month to book a flight from Philadelphia to Boulder?

Currently, October is the cheapest month in which you can book a flight from Philadelphia to Boulder (average of $197). Flying from Philadelphia to Boulder 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 PHL to BD9?

Find hourly flight availability from Philadelphia to Boulder. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated September 14, 2025.

Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Philadelphia to Boulder as you normally would.

What is the cheapest day to fly from Philadelphia to Boulder?

Use this chart to determine the cheapest time to fly round-trip from Philadelphia to Boulder. Price data was last updated on December 16, 2024.

Travelers seeking maximum savings on their Philadelphia to Boulder flight should consider departing on Tuesday evenings when fares are most often at their lowest. Sunday afternoons flights should be avoided if possible as fares are typically the most expensive at this time.

Weekly flight availability from Philadelphia to Boulder

Explore weekly flight availability from Philadelphia to Boulder. Discover flights operating on different days of the week, giving you the flexibility to choose a travel day that best fits your plans. Compare info to find the most convenient option for your journey. Data last updated September 14, 2025.

The most flights from PHL to BD9 are scheduled on a Monday (16 on average). You will have fewer flight options on Wednesday, which is when the least amount of flights are scheduled (10 on average).

Reviews of airlines servicing Boulder

Get insights into the airlines that provide service to Boulder. 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 Boulder. Reviews last updated September 14, 2025.
Read through reviews of airlines operating flights from Philadelphia to Boulder, such as Southwest, Delta, and United Airlines. Reviews also offer insight into each airline's entertainment options, comfort, food, crew/service, and boarding process.
Southwest
8.0
Very good
4,245 reviews

Boarding

8.1

Food

7.0

Overall

8.0

Crew

8.6

Entertainment

7.5

Comfort

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
4,245 reviews
Southwest
8.0
Very good
4,245 reviews

Boarding

8.1

Food

7.0

Overall

8.0

Crew

8.6

Entertainment

7.5

Comfort

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
Delta
8.0
Very good
7,956 reviews
Southwest
8.0
Very good
4,245 reviews

Boarding

8.1

Food

7.0

Overall

8.0

Crew

8.6

Entertainment

7.5

Comfort

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
United Airlines
7.4
Good
8,931 reviews
Southwest
8.0
Very good
4,245 reviews

Boarding

8.1

Food

7.0

Overall

8.0

Crew

8.6

Entertainment

7.5

Comfort

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
American Airlines
7.2
Good
10,000 reviews
Southwest
8.0
Very good
4,245 reviews

Boarding

8.1

Food

7.0

Overall

8.0

Crew

8.6

Entertainment

7.5

Comfort

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
3,173 reviews
Southwest
8.0
Very good
4,245 reviews

Boarding

8.1

Food

7.0

Overall

8.0

Crew

8.6

Entertainment

7.5

Comfort

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 Philadelphia to Boulder. Access travel guides, tips, and recommendations to enhance your travel experience. Get information about local attractions, weather, transportation options, and more.

  • What airport do you fly from for flights from Philadelphia to Boulder?

    If you book a flight to Boulder from Philadelphia, you will be flying from Philadelphia, which is the city’s only airport. Philadelphia (PHL) is located 7.0 mi from the center of Philadelphia. There are 13 flights from Philadelphia to Boulder per day from 8 different airlines.

  • How popular is this Philadelphia to Boulder flight route?

    This flight path from Philadelphia to Boulder was viewed by 118 users in the past month. Keep an eye out for changes in search interest prior to high and low season.

  • How long is the flight from Philadelphia to Boulder?

    Departing from Philadelphia to Boulder will take you 7h 32m. The distance between Philadelphia and Boulder is about 1553 mi. Both multi-stop and nonstop flights can be found to your destination and back.

  • What are the most reliable airlines from Philadelphia to Boulder?

    The top 3 most reliable airlines when flying from Philadelphia to Boulder are Air Canada (79%), Qatar Airways (77%) and United Airlines (77%).

  • What are the cheapest flights from Philadelphia to Boulder?

    On average you can expect to pay $667 for a flight from Philadelphia to Boulder. The cheapest flight overall is $86 while the most popular route, (Philadelphia - Denver Intl) is currently priced at $147.

  • Can I find deals for flights from Philadelphia to Boulder that include hotel bookings?

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

  • How can I find direct flights from Philadelphia to Boulder?

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

  • Can I find deals for business class flights from Philadelphia to Boulder?

    Yes. Cheapflights offers flight deals from Philadelphia to Boulder 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 Philadelphia to Boulder?

    Currently, October is the cheapest month in which you can book a flight from Philadelphia to Boulder (average of $197). Flying from Philadelphia to Boulder 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

Browse thousands of different options on Cheapflights for your next trip

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Alternative routes for Philadelphia to Boulder

See prices for flight routes from nearby airports that may be better suited for you.
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Top 8 airlines flying from Philadelphia to Boulder

Discover the top 8 airlines that operate flights from Philadelphia to Boulder. 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 14, 2025.
AirlineCheapestAverageFlexibilityOn-time
Allegiant AirCheapest$106Average$197FlexibilityNo cancel feeOn-time88%
FrontierCheapest$111Average$229FlexibilityNo cancel feeOn-time62%
DeltaCheapest$134Average$380FlexibilityNo cancel feeOn-timeN/A
SouthwestCheapest$193Average$409FlexibilityNo cancel feeOn-time63%
United AirlinesCheapest$195Average$495FlexibilityNo cancel feeOn-time69%
American AirlinesCheapest$196Average$416FlexibilityNo cancel feeOn-time71%
JetBlueCheapest$207Average$314FlexibilityNo cancel feeOn-time62%
Sun Country AirCheapest$251Average$280FlexibilityNo cancel feeOn-time83%

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