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$99+ 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 9/3. Fares are subject to change and may not be available on all flights or dates of travel.
PHL — DEN
Jun 17 — Jun 241
Tue 6/17
Tue 6/24
1 adult, Economy
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Cheapflights Tip: The best prices from Philadelphia to Boulder are usually found in September or October, booked 78 days in advance, depart on a Wednesday or Tuesday 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 June 12, 2025.

Round-trip from

$171
(Cheapflightsfares)

One-way from

$99
(United Airlines)

Popular in

December

Cheapest in

September

Average price

$288
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. 2% potential price decrease ($8 potential savings vs. average RT price).
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Average for round-trip flights in June 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 June 12, 2025.

This Cheapflightsfares deal was found by Cheapflights users on 6/11. 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.
Sat 8/166:15 amPHL - DEN
Nonstop4h 13mFrontier
Wed 8/2011:15 pmDEN - PHL
Nonstop3h 39mFrontier
Deal found 6/11$171
This American Airlines deal was found by Cheapflights users on 6/11. 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.
Wed 10/18:33 amPHL - DEN
Nonstop4h 04mAmerican Airlines
Wed 10/12:13 pmDEN - PHL
Nonstop3h 48mAmerican Airlines
Deal found 6/11$192
This Southwest deal was found by Cheapflights users on 6/11. 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.
Tue 9/234:45 pmPHL - DEN
Nonstop4h 00mSouthwest
Sat 9/2711:05 amDEN - PHL
Nonstop3h 35mSouthwest
Deal found 6/11$212
This Delta deal was found by Cheapflights users on 6/10. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 8/95:21 pmPHL - DEN
1 stop7h 08mDelta
Sat 8/164:00 pmDEN - PHL
1 stop5h 50mDelta
Deal found 6/10$257
This JetBlue deal was found by Cheapflights users on 6/11. 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 JetBlue is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 10/23:10 pmPHL - DEN
1 stop8h 39mJetBlue
Sun 10/510:44 pmDEN - PHL
1 stop8h 38mJetBlue
Deal found 6/11$283
This United Airlines deal was found by Cheapflights users on 6/11. 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.
Tue 8/268:00 amPHL - DEN
Nonstop4h 04mUnited Airlines
Sun 8/3111:59 pmDEN - PHL
Nonstop3h 36mUnited Airlines
Deal found 6/11$312

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 June 12, 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

Sat 8/16

6:15 am-8:28 am

Nonstop4h 13m

Denver Intl

Wed 8/20

11:15 pm-4:54 am

Nonstop3h 39m

$171

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Wed 10/1

8:33 am-10:37 am

Nonstop4h 04m

Denver Intl

Wed 10/1

2:13 pm-8:01 pm

Nonstop3h 48m

$192

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Tue 9/23

4:45 pm-6:45 pm

Nonstop4h 00m

Denver Intl

Sat 9/27

11:05 am-4:40 pm

Nonstop3h 35m

$212

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Sat 8/9

5:21 pm-10:29 pm

1 stop7h 08m

Denver Intl

Sat 8/16

4:00 pm-11:50 pm

1 stop5h 50m

$257

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Thu 10/2

3:10 pm-9:49 pm

1 stop8h 39m

Denver Intl

Sun 10/5

10:44 pm-9:22 am

1 stop8h 38m

$283

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Tue 8/26

8:00 am-10:04 am

Nonstop4h 04m

Denver Intl

Sun 8/31

11:59 pm-5:35 am

Nonstop3h 36m

$312

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Wed 9/3

3:40 pm-5:53 pm

Nonstop4h 13m

$99

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Tue 8/12

10:55 am-1:01 pm

Nonstop4h 06m

$109

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Sun 9/7

8:15 am-1:42 pm

1 stop7h 27m

$116

PhiladelphiaDenver

PHL - DEN

PHLDEN

Philadelphia

Fri 9/5

3:10 pm-9:49 pm

1 stop8h 39m

$125

Flights are sorted by cheapest round-trip flights first.

Deals found on 6/12

Showing 1-10 of 15 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 June 9, 2025.

Booking 78 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 June 12, 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. Monday 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 June 12, 2025.

The most flights from PHL to BD9 are scheduled on a Thursday (16 on average). You will have fewer flight options on Saturday, which is when the least amount of flights are scheduled (6 on average).

Rainfall in Boulder by month

Plan your trip to Boulder by taking into account the average rainfall totals by month.

In terms of precipitation, rainfall in Boulder ranges from 0.5 - 2.3 inches per month. May is typically the wettest month, when rainfall can reach 2.3 in. January is typically the driest time to visit Boulder when rainfall is around 0.5 in.

Temperature in Boulder by month

Plan your trip to Boulder by taking into account the average temperature totals by month.

If weather is an important factor for your trip to Boulder, use this chart to help with planning. For those seeking warmer temperatures, July is the ideal time of year to visit, when temperatures reach an average of 73.4 F. Travelers looking to avoid the cold should look outside of January, when temperatures are typically at their lowest (around 30.2 F).

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 June 12, 2025.
Read reviews from past customers who have flown Alaska Airlines, Southwest and Delta from Philadelphia to Boulder. You can also see how each airline compares in terms of entertainment options, comfort, food, crew/service, and boarding process.
Alaska Airlines
8.0
Very good
10,000 reviews

Entertainment

7.1

Crew

8.5

Overall

8.0

Comfort

7.8

Boarding

8.1

Food

7.1

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.
Alaska Airlines
8.0
Very good
10,000 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Entertainment

7.1

Crew

8.5

Overall

8.0

Comfort

7.8

Boarding

8.1

Food

7.1

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.
Southwest
8.0
Very good
4,287 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Entertainment

7.1

Crew

8.5

Overall

8.0

Comfort

7.8

Boarding

8.1

Food

7.1

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.
Delta
8.0
Very good
7,950 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Entertainment

7.1

Crew

8.5

Overall

8.0

Comfort

7.8

Boarding

8.1

Food

7.1

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.
United Airlines
7.4
Good
8,790 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Entertainment

7.1

Crew

8.5

Overall

8.0

Comfort

7.8

Boarding

8.1

Food

7.1

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.
JetBlue
7.3
Good
2,925 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Entertainment

7.1

Crew

8.5

Overall

8.0

Comfort

7.8

Boarding

8.1

Food

7.1

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.

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 12 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 153 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 $99. Users have also found prices from $109 and $116 on American Airlines and Frontier, 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 (79%), Frontier (71%) and Southwest (66%).

  • What are the cheapest flights from Philadelphia to Boulder?

    On average you can expect to pay $768 for a flight from Philadelphia to Boulder. The cheapest flight overall is $92 while the most popular route, (Philadelphia - Denver Intl) is currently priced at $197.

  • 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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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 June 12, 2025.
AirlineCheapestAverageFlexibilityOn-time
Sun Country AirCheapest$82Average$275FlexibilityNo cancel feeOn-time83%
FrontierCheapest$87Average$214FlexibilityNo cancel feeOn-time62%
DeltaCheapest$134Average$366FlexibilityNo cancel feeOn-timeN/A
Allegiant AirCheapest$154Average$216FlexibilityNo cancel feeOn-time88%
American AirlinesCheapest$182Average$415FlexibilityNo cancel feeOn-time71%
United AirlinesCheapest$188Average$496FlexibilityNo cancel feeOn-time69%
SouthwestCheapest$194Average$411FlexibilityNo cancel feeOn-time63%
JetBlueCheapest$207Average$325FlexibilityNo cancel feeOn-time62%

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