$96+ 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 3/2. Fares are subject to change and may not be available on all flights or dates of travel.
PHL — DEN
feb. 28 — mar. 71
1 adult, Economy
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Find cheap flights from Philadelphia to Boulder with Cheapflights
1. Tell us where you want to go
Enter your travel information like dates, passengers, trip type (one-way or round trip), and preferred cabin class then click “Find deals”2. Select your favorite providers
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Review each provider’s pricing and select the best option for you! Book through your favorite provider’s website for a seamless experience.Cheapflights Tip: The best prices from Philadelphia to Boulder are usually found in July or August, booked 55 days in advance, depart on a Friday or Thursday and return on a Wednesday
Cheap flight deals from Philadelphia to Boulder
Cheapest flights from Philadelphia to BoulderExplore 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 enero 29, 2026.
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 enero 29, 2026.
This Frontier deal was found by Cheapflights users on 1/27. 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.
dom. 2/225:42 pm
PHL
- DEN
Nonstop4h 30m
Frontier
mar. 3/312:59 am
DEN
- PHL
1 stop7h 25m
Frontier
Deal found 1/27![Frontier logo]()
$154
This Trip.com deal was found by Cheapflights users on 1/28. 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.
mié. 2/2511:40 am
PHL
- DEN
1 stop11h 55m
Multiple Airlines
mié. 3/42:15 pm
DEN
- PHL
2 stops16h 29m
Multiple Airlines
Deal found 1/28![Multiple Airlines logo]()
$155
This Cheapflightsfares deal was found by Cheapflights users on 1/27. 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.
mié. 2/2511:40 am
PHL
- DEN
1 stop11h 55m
Frontier
lun. 3/211:59 pm
DEN
- PHL
1 stop10h 40m
Frontier
Deal found 1/27![Frontier logo]()
$157
This Cheapflightsfares deal was found by Cheapflights users on 1/27. 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.
jue. 2/265:47 pm
PHL
- DEN
Nonstop4h 30m
Frontier
jue. 3/511:05 am
DEN
- PHL
Nonstop3h 32m
Frontier
Deal found 1/27![Frontier logo]()
$158
This Kiwi.com deal was found by Cheapflights users on 1/27. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
mié. 2/256:10 pm
PHL
- DEN
1 stop17h 21m
Multiple Airlines
mar. 3/31:42 pm
DEN
- PHL
2 stops17h 02m
Multiple Airlines
Deal found 1/27![Multiple Airlines logo]()
$159
This Kiwi.com deal was found by Cheapflights users on 1/28. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
dom. 3/15:30 am
PHL
- DEN
1 stop18h 40m
Frontier
jue. 3/511:05 am
DEN
- PHL
Nonstop3h 32m
Frontier
Deal found 1/28![Frontier logo]()
$160
This Kiwi.com deal was found by Cheapflights users on 1/27. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
mié. 2/1812:21 pm
PHL
- DEN
1 stop23h 10m
Frontier
mié. 2/258:00 pm
DEN
- PHL
1 stop16h 35m
Frontier
Deal found 1/27![Frontier logo]()
$161
This Kiwi.com deal was found by Cheapflights users on 1/26. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
sáb. 2/2811:52 am
PHL
- DEN
1 stop11h 43m
Frontier
lun. 3/91:09 pm
DEN
- PHL
1 stop9h 43m
Frontier
Deal found 1/26![Frontier logo]()
$162
This Kiwi.com deal was found by Cheapflights users on 1/28. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
mié. 3/46:00 am
PHL
- DEN
2 stops17h 35m
Multiple Airlines
dom. 3/811:59 pm
DEN
- PHL
Nonstop3h 32m
Multiple Airlines
Deal found 1/28![Multiple Airlines logo]()
$163
This Frontier deal was found by Cheapflights users on 1/27. 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.
lun. 2/235:47 pm
PHL
- DEN
Nonstop4h 30m
Frontier
lun. 3/211:05 am
DEN
- PHL
1 stop9h 47m
Frontier
Deal found 1/27![Frontier logo]()
$164
This Kiwi.com deal was found by Cheapflights users on 1/27. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
dom. 3/15:30 am
PHL
- DEN
1 stop18h 40m
Frontier
vie. 3/611:59 pm
DEN
- PHL
Nonstop3h 32m
Frontier
Deal found 1/27![Frontier logo]()
$165
This Frontier deal was found by Cheapflights users on 1/28. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
lun. 3/308:25 pm
PHL
- DEN
Nonstop4h 39m
Frontier
dom. 4/511:56 pm
DEN
- PHL
Nonstop3h 35m
Frontier
Deal found 1/28![Frontier logo]()
$166
Find flight deals from Philadelphia to Boulder
Keep the following information in mind while searching for Philadelphia to Boulder flight deals. Data was last updated enero 29, 2026.
Most accurate provider | FlightHub 3 stars |
|---|---|
Most trusted provider | FlightHub 3 stars |
Round-trip from | $154 (Frontier) |
One-way from | $96 (Cheapflightsfares) |
Popular in | December |
Cheapest in | July |
Average price | $332 |
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 enero 29, 2026.
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
mié. 2/25
5:00 pm-7:20 pm
Nonstop4h 20m
Denver Intl
mié. 3/4
4:35 pm-10:00 pm
Nonstop3h 25m
$211
PhiladelphiaDenver
PHL - DEN
PHLDEN
Philadelphia
lun. 3/9
3:30 pm-6:00 pm
Nonstop4h 30m
Denver Intl
mié. 3/11
5:57 pm-11:32 pm
Nonstop3h 35m
$228
PhiladelphiaDenver
PHL - DEN
PHLDEN
Philadelphia
sáb. 2/28
5:40 pm-8:00 pm
Nonstop4h 20m
Denver Intl
mié. 3/4
6:50 am-5:25 pm
1 stop8h 35m
$229
PhiladelphiaDenver
PHL - DEN
PHLDEN
Philadelphia
dom. 2/22
9:41 am-1:35 pm
1 stop5h 54m
Denver Intl
jue. 3/5
7:20 am-3:50 pm
1 stop6h 30m
$273
PhiladelphiaDenver
PHL - DEN
PHLDEN
Philadelphia
sáb. 3/7
5:05 pm-7:25 pm
Nonstop4h 20m
Denver Intl
mié. 3/11
12:25 pm-9:55 pm
1 stop7h 30m
$287
PhiladelphiaDenver
PHL - DEN
PHLDEN
Philadelphia
mar. 3/3
5:00 pm-7:20 pm
Nonstop4h 20m
Denver Intl
sáb. 3/7
8:10 am-5:30 pm
1 stop7h 20m
$289
PhiladelphiaDenver
PHL - DEN
PHLDEN
Philadelphia
sáb. 2/28
4:00 pm-8:35 pm
1 stop6h 35m
Denver Intl
sáb. 3/7
7:00 pm-12:20 am
Nonstop3h 20m
$289
PhiladelphiaDenver
PHL - DEN
PHLDEN
Philadelphia
vie. 4/10
6:08 pm-7:00 am
2 stops14h 52m
Denver Intl
sáb. 4/11
10:20 am-8:51 pm
1 stop8h 31m
$290
PhiladelphiaDenver
PHL - DEN
PHLDEN
Philadelphia
mar. 2/24
3:37 pm-6:07 pm
Nonstop4h 30m
Denver Intl
mar. 3/3
5:57 pm-11:32 pm
Nonstop3h 35m
$301
PhiladelphiaDenver
PHL - DEN
PHLDEN
Philadelphia
dom. 3/8
6:54 pm-11:39 pm
1 stop6h 45m
Denver Intl
vie. 3/13
6:15 pm-5:41 am
1 stop9h 26m
$308
Showing 1-10 of 23 results
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 January 23, 2026.
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 $88). Flying from Philadelphia to Boulder in May is currently the most expensive (average of $140). 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 enero 29, 2026.
Unlike in the afternoon, when flights are generally more expensive, you can save up to 34% on flights from Philadelphia to Boulder by exploring options for tickets at noon.
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 January 24, 2026.
Travelers seeking maximum savings on their Philadelphia to Boulder flight should consider departing on Friday at noon 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 enero 29, 2026.
The most flights from PHL to BD9 are scheduled on a Monday (9 on average). You will have fewer flight options on Friday, which is when the least amount of flights are scheduled (6 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 enero 29, 2026.
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.
Boarding
8.1
Food
7.0
Overall
8.0
Crew
8.6
Entertainment
7.5
Comfort
8.0
Reviews
1 / 20
2.0
MediocreThomas,Dec 2025
SEA - DEN
Boarding
8.1
Food
7.0
Overall
8.0
Crew
8.6
Entertainment
7.5
Comfort
8.0
Reviews
1 / 20
2.0
MediocreThomas,Dec 2025
SEA - DEN
Boarding
8.1
Food
7.0
Overall
8.0
Crew
8.6
Entertainment
7.5
Comfort
8.0
Reviews
1 / 20
2.0
MediocreThomas,Dec 2025
SEA - DEN
Boarding
8.1
Food
7.0
Overall
8.0
Crew
8.6
Entertainment
7.5
Comfort
8.0
Reviews
1 / 20
2.0
MediocreThomas,Dec 2025
SEA - DEN
Boarding
8.1
Food
7.0
Overall
8.0
Crew
8.6
Entertainment
7.5
Comfort
8.0
Reviews
1 / 20
2.0
MediocreThomas,Dec 2025
SEA - DEN
Boarding
8.1
Food
7.0
Overall
8.0
Crew
8.6
Entertainment
7.5
Comfort
8.0
Reviews
1 / 20
2.0
MediocreThomas,Dec 2025
SEA - DEN
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.
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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.
Top 7 airlines flying from Philadelphia to Boulder
Discover the top 7 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 enero 29, 2026.
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$106 | Average$194 | FlexibilityNo cancel fee | On-time88% | |
| Cheapest$108 | Average$220 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$128 | Average$383 | FlexibilityNo cancel fee | On-timeN/A | |
| Cheapest$188 | Average$438 | FlexibilityNo cancel fee | On-time69% | |
| Cheapest$199 | Average$410 | FlexibilityNo cancel fee | On-time63% | |
| Cheapest$204 | Average$422 | FlexibilityNo cancel fee | On-time71% | |
| Cheapest$208 | Average$268 | FlexibilityNo cancel fee | On-time62% |