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$110+ 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 9/22. Fares are subject to change and may not be available on all flights or dates of travel.
PHL — DEN
Aug 4 — Aug 111
Mon 8/4
Mon 8/11
1 adult, Economy
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Cheapflights Tip: The best prices from Philadelphia to Boulder are usually found in September or October, booked 33 days in advance, depart on a Wednesday or Friday and return on a Wednesday

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 July 30, 2025.

Round-trip from

$187
(Cheapflightsfares)

One-way from

$110
(Trip.com)

Popular in

December

Cheapest in

September

Average price

$286
From Philadelphia to Boulder
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One-way flight from Philadelphia to Boulder
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Highest demand for flights based on searches. 5% potential increase in price ($16 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).
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Average for round-trip flights in July 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 July 30, 2025.

This Cheapflightsfares deal was found by Cheapflights users on 7/29. 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 8/151:02 pmPHL - DEN
Nonstop4h 19mFrontier
Sun 8/1711:30 pmDEN - PHL
Nonstop3h 39mFrontier
Deal found 7/29$187
This American Airlines deal was found by Cheapflights users on 7/30. 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 American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 8/307:35 pmPHL - DEN
Nonstop4h 20mAmerican Airlines
Sat 9/67:00 amDEN - PHL
Nonstop3h 36mAmerican Airlines
Deal found 7/30$196
This Southwest deal was found by Cheapflights users on 7/28. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 9/177:45 amPHL - DEN
Nonstop3h 50mSouthwest
Sun 9/216:55 pmDEN - PHL
Nonstop3h 35mSouthwest
Deal found 7/28$217
This Trip.com deal was found by Cheapflights users on 7/28. 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 Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 10/143:10 pmPHL - DEN
1 stop8h 39mJetBlue
Fri 10/1710:44 pmDEN - PHL
1 stop8h 38mJetBlue
Deal found 7/28$233

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 July 30, 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

Fri 8/15

1:02 pm-3:21 pm

Nonstop4h 19m

Denver Intl

Sun 8/17

11:30 pm-5:09 am

Nonstop3h 39m

$187

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Sat 8/30

7:35 pm-9:55 pm

Nonstop4h 20m

Denver Intl

Sat 9/6

7:00 am-12:36 pm

Nonstop3h 36m

$196

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Wed 9/17

7:45 am-9:35 am

Nonstop3h 50m

Denver Intl

Sun 9/21

6:55 pm-12:30 am

Nonstop3h 35m

$217

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Tue 10/14

3:10 pm-9:49 pm

1 stop8h 39m

Denver Intl

Fri 10/17

10:44 pm-9:22 am

1 stop8h 38m

$233

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Mon 9/22

1:58 pm-8:47 pm

1 stop8h 49m

$110

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Thu 10/2

6:45 am-8:57 am

Nonstop4h 12m

$111

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Tue 8/19

7:35 pm-9:55 pm

Nonstop4h 20m

$116

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Sun 9/21

8:00 am-10:04 am

Nonstop4h 04m

$119

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Fri 9/5

3:10 pm-10:34 pm

1 stop9h 24m

$125

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Sat 9/6

2:20 pm-9:05 pm

1 stop8h 45m

$126

Flights are sorted by cheapest round-trip flights first.

Deals found on 7/29

Showing 1-10 of 12 results
1
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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 July 25, 2025.

Booking 33 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 July 30, 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 Saturday 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 July 30, 2025.

The most flights from PHL to BD9 are scheduled on a Tuesday (18 on average). You will have fewer flight options on Sunday, which is when the least amount of flights are scheduled (4 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 July 30, 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
4,241 reviews

Boarding

8.1

Comfort

8.0

Crew

8.6

Overall

8.0

Food

7.0

Entertainment

7.5

Reviews

1 / 20
8.0
Excellent

Gina,Jul 2025

LAS - DEN

We experienced bad weather, which turned our 1.5 hour flight from Las Vegas to Denver, into 3.5. The pilot and crew kept us updated and explained that we had to circle and or possibly redirect to another airport. After circling for sometime, we were able to land smoothly in Denver. Thank you to all the flight crew, tower control, and all who got us to our destination safely.
Southwest
8.0
Very good
4,241 reviews
Southwest
8.0
Very good
4,241 reviews

Boarding

8.1

Comfort

8.0

Crew

8.6

Overall

8.0

Food

7.0

Entertainment

7.5

Reviews

1 / 20
8.0
Excellent

Gina,Jul 2025

LAS - DEN

We experienced bad weather, which turned our 1.5 hour flight from Las Vegas to Denver, into 3.5. The pilot and crew kept us updated and explained that we had to circle and or possibly redirect to another airport. After circling for sometime, we were able to land smoothly in Denver. Thank you to all the flight crew, tower control, and all who got us to our destination safely.
Delta
8.0
Very good
7,980 reviews
Southwest
8.0
Very good
4,241 reviews

Boarding

8.1

Comfort

8.0

Crew

8.6

Overall

8.0

Food

7.0

Entertainment

7.5

Reviews

1 / 20
8.0
Excellent

Gina,Jul 2025

LAS - DEN

We experienced bad weather, which turned our 1.5 hour flight from Las Vegas to Denver, into 3.5. The pilot and crew kept us updated and explained that we had to circle and or possibly redirect to another airport. After circling for sometime, we were able to land smoothly in Denver. Thank you to all the flight crew, tower control, and all who got us to our destination safely.
United Airlines
7.4
Good
8,896 reviews
Southwest
8.0
Very good
4,241 reviews

Boarding

8.1

Comfort

8.0

Crew

8.6

Overall

8.0

Food

7.0

Entertainment

7.5

Reviews

1 / 20
8.0
Excellent

Gina,Jul 2025

LAS - DEN

We experienced bad weather, which turned our 1.5 hour flight from Las Vegas to Denver, into 3.5. The pilot and crew kept us updated and explained that we had to circle and or possibly redirect to another airport. After circling for sometime, we were able to land smoothly in Denver. Thank you to all the flight crew, tower control, and all who got us to our destination safely.
JetBlue
7.3
Good
2,913 reviews
Southwest
8.0
Very good
4,241 reviews

Boarding

8.1

Comfort

8.0

Crew

8.6

Overall

8.0

Food

7.0

Entertainment

7.5

Reviews

1 / 20
8.0
Excellent

Gina,Jul 2025

LAS - DEN

We experienced bad weather, which turned our 1.5 hour flight from Las Vegas to Denver, into 3.5. The pilot and crew kept us updated and explained that we had to circle and or possibly redirect to another airport. After circling for sometime, we were able to land smoothly in Denver. Thank you to all the flight crew, tower control, and all who got us to our destination safely.
American Airlines
7.2
Good
10,000 reviews
Southwest
8.0
Very good
4,241 reviews

Boarding

8.1

Comfort

8.0

Crew

8.6

Overall

8.0

Food

7.0

Entertainment

7.5

Reviews

1 / 20
8.0
Excellent

Gina,Jul 2025

LAS - DEN

We experienced bad weather, which turned our 1.5 hour flight from Las Vegas to Denver, into 3.5. The pilot and crew kept us updated and explained that we had to circle and or possibly redirect to another airport. After circling for sometime, we were able to land smoothly in Denver. Thank you to all the flight crew, tower control, and all who got us to our destination safely.

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 11 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 128 users in the past month. Keep an eye out for changes in search interest prior to high and low season.

  • What are the cheapest airlines to fly from Philadelphia to Boulder one-way?

    For one-way options, check prices for United Airlines. According to our data, you can fly for as low as $116. Users have also found prices from $117 and $125 on Frontier and JetBlue, respectively.

  • 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 (72%), United Airlines (68%) and Qatar Airways (66%).

  • What are the cheapest flights from Philadelphia to Boulder?

    On average you can expect to pay $850 for a flight from Philadelphia to Boulder. The cheapest flight overall is $94 while the most popular route, (Philadelphia - Denver Intl) is currently priced at $165.

  • 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

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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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Philadelphia to Aspen flights

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 July 30, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$103Average$224FlexibilityNo cancel feeOn-time62%
Allegiant AirCheapest$106Average$205FlexibilityNo cancel feeOn-time88%
DeltaCheapest$134Average$366FlexibilityNo cancel feeOn-timeN/A
American AirlinesCheapest$186Average$411FlexibilityNo cancel feeOn-time71%
SouthwestCheapest$191Average$404FlexibilityNo cancel feeOn-time63%
United AirlinesCheapest$193Average$506FlexibilityNo cancel feeOn-time69%
JetBlueCheapest$207Average$325FlexibilityNo cancel feeOn-time62%
Sun Country AirCheapest$251Average$275FlexibilityNo cancel feeOn-time83%

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