Route reliability record
PHL→DEN
Philadelphia to Denver
- Flights
- 3,060
- Period
- September 2025 to August 2026
- Distance
- 1,558 mi
- Carriers
- 4
This route sits in the middle of the pack with a C. Close to three flights in four arrive on time by the DOT's definition, 4 points worse than the national rate of 77.3%. The late ones land a little over an hour behind schedule. That rests on 3,060 PHL to DEN flights, of which United Airlines flew 953 at 81.9% on time.
Best time to fly PHL to DEN: a 5am–8am departure, ideally on a Wednesday. Flights in that window arrived on time 84.6% of the time and Wednesday flights 75.2%, against 73.3% for the route overall.
United Airlines is the most reliable of the three carriers covered here at 81.9% on time across 953 flights.
Key figures
On time
73.3%
Arrivals under 15 minutes late, of 2,997 completed flights
Avg delay
73 min
Across delayed arrivals only, not all flights
Cancelled
1.54%
National rate is 1.89%
Best carrier
United
81.9% on time across 953 flights
These figures cover 3,060 flights between September 2025 and August 2026. Beyond the headline rate, 9.3% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Which airline is most reliable on PHL to DEN
The choice of carrier is not cosmetic here. United Airlines arrives on time 81.9% of the time; Southwest Airlines manages 65.8%. Sample sizes sit next to every figure, because a two-point gap across 880 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 953 | 81.9% | 82 min | 0.73% | B+ |
| American Airlines | 926 | 74.0% | 66 min | 2.05% | C |
| Southwest Airlines | 880 | 65.8% | 57 min | 1.14% | C |
| Frontier Airlinesthin sample | 301 | 65.3% | 120 min | 3.65% | C− |
The spread between United and Southwest is 16 points, wide enough that it should decide the booking. On a hundred trips that is 16 more arrivals inside the on-time window.
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Best ways to make this trip
The most reliable ways to fly Philadelphia to Denver
Every airline on this route, ranked by how often a scheduled flight actually operated and arrived on time, with its best departure time and most punctual flight number. No nearby airport pair beat these.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. PHL → DENPhiladelphia to Denver | United Airlines | 81.3% | 81.9% | 0.73% | 8am–11am, Wed | — |
| 2. PHL → DENPhiladelphia to Denver | American Airlines | 72.5% | 74.0% | 2.05% | 11am–2pm, Tue | — |
| 3. PHL → DENPhiladelphia to Denver | Southwest Airlines | 65.0% | 65.8% | 1.14% | 5am–8am, Sun | — |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 27 points, against 16 points between the best and worst carrier.
- 5am–8am440 flights84.6%
- 8am–11am858 flights84.2%
- 11am–2pm411 flights72.3%
- 2pm–5pm527 flights66.9%
- 5pm–8pm460 flights57.5%
- 8pm–5am364 flights62.8%
Scale runs 50% to 90%.
The 5pm–8pm window is where this operation falls apart: 57.5% on time, against 84.6% for the 5am–8am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 8am–11am window is the busiest, with 858 flights scheduled in it.
Explore
Filter PHL to DEN by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On PHL to DEN, the best departure window is 5am–8am at 84.6% on time and the worst is 5pm–8pm at 57.5%, a wide gap of 27.1 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am84.6%
- 8–11am84.2%
- 11am–2pm72.3%
- 2–5pm66.9%
- 5–8pm57.5%
- 8pm–5am62.8%
best all US flightsScale 50% to 95%.
Across the year
When delays peak on this route
This route's year swings by 30 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
December is the weak month at 55.6% on time, against 85.7% in November. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. July was the busiest month here, with 345 flights.
Across the week, Wednesday is the strongest day at 75.2% on time and Monday the weakest at 71.2%, a spread of 4 points.
Delay causes
Why this route gets delayed
Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 58,000 reported delay minutes.
- 36%Late-arriving aircraft
- 33%Carrier
- 25%National Airspace System
- 6%Extreme weather
- 0%Security
36% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 58,000 reported delay minutes here, that single category outweighs weather by 6 to one. The split is drawn from 58,272 reported delay minutes.
The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 84.6% on time here.
Cancellations sit at 1.54% against a national 1.89%, which is ordinary. Diversions add another 0.52%.
Connections and stage length
What a delay here actually costs
9.3% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection here, and two hours if the onward flight is on a separate ticket.
At 1,558 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.
The return leg runs 72.8% on time across 3,056 flights, within half a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 3,060 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.
Work out the risk of missing a connection in DEN after this flight
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. November runs 85.7% on time and December 55.6%, a swing of 30 points. If the dates move at all, move them out of December before you think about anything else. 2,997 completed flights over 12 months sit behind that.
Common questions
PHL to DEN questions
How often is PHL to DEN delayed?
About one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 26.7% of the 3,060 flights in this analysis, against 22.7% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on PHL to DEN?
United Airlines leads at 81.9% on time across 953 flights. Southwest Airlines is at the other end on 65.8%, a gap of 16 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on PHL to DEN?
The 5am–8am departure window is the strongest at 84.6% on time. The 5pm–8pm window is the weakest at 57.5%, 27 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are December delays on PHL to DEN?
December is the weakest month at 55.6% on time, compared with 85.7% in November. Across the year that is 30 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- DEN to PHL — the return legseparate record
- Philadelphia International (PHL) delay statistics
- Denver International (DEN) delay statistics
- United Airlines on PHL to DEN81.9%
- American Airlines on PHL to DEN74.0%
- Southwest Airlines on PHL to DEN65.8%
- Frontier Airlines on PHL to DEN65.3%
- PHL to ATL, a related route78.0%
- PHX to DEN, a related route76.7%
- PHL to MCO, a related route72.4%
- United Airlines on-time record81.9%
- American Airlines on-time record74.0%
- Southwest Airlines on-time record65.8%
- Why the first flight of the morning is statistically safest
- Same route, different airline: where the carrier you pick matters most
Direction matters. PHL to DEN and DEN to PHL are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.