Carrier route record
WNPHL→DEN
Southwest Airlines · Philadelphia to Denver
- Flights
- 879
- Period
- July 2025 to June 2026
- Share of route
- 29%
- Carriers
- 4
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on PHL to DEN sits in the middle of the pack with a C+. About seven flights in ten arrive on time by the DOT's definition, 9 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 879 flights. The strongest carrier on the route with a full sample, United Airlines, flew 953 at 83.9% on time.
The national on-time rate over the same period is 77.6%, so Southwest on PHL to DEN runs 9 points behind the country as a whole. Across a thousand flights that is about 86 extra late arrivals.
Key figures
On time
69.0%
Arrivals under 15 minutes late, of 864 completed flights
Avg delay
57 min
Across delayed arrivals only, not all flights
Cancelled
0.80%
National rate is 1.81%
Whole route
74.9%
Every carrier on PHL to DEN, 3,005 flights
These figures cover 879 flights between July 2025 and June 2026. Beyond the headline rate, 8.7% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
Carrier by carrier
Southwest against every carrier on PHL to DEN
Southwest flew 879 of the 3,005 flights on PHL to DEN, about 29% of it. Its 69.0% on time is 6 points worse than the route as a whole, which runs 74.9%. Ranked by on-time rate it is number three of four carriers on the route, where the range runs from United at 83.9% to Frontier at 68.4%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The choice of carrier is not cosmetic here. United Airlines arrives on time 83.9% of the time; American Airlines manages 73.3%. Sample sizes sit next to every figure, because a two-point gap across 877 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 953 | 83.9% | 92 min | 0.84% | B+ |
| American Airlines | 877 | 73.3% | 66 min | 1.60% | C |
| Southwest Airlines (this page) | 879 | 69.0% | 57 min | 0.80% | C+ |
| Frontier Airlinesthin sample | 296 | 68.4% | 112 min | 1.69% | C |
United leads American by 11 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
Departure window
When Southwest runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 35 points, against 11 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am352 flights84.8%
- 8am–11am3 flights—
- 11am–2pm142 flights66.7%
- 2pm–5pm128 flights64.5%
- 5pm–8pm254 flights50.0%
- 8pm–5am—
Scale runs 40% to 90%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 50.0% on time, against 84.8% 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 5am–8am window is the busiest, with 352 flights scheduled in it.
Across the year
Southwest on PHL to DEN through the year
December is the weak month at 44.0% on time, against 81.7% in April. 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. August was the busiest month here, with 91 flights.
Across the week, Tuesday is the strongest day at 71.0% on time and Thursday the weakest at 66.4%. 5 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Southwest runs late on this route
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 15,000 reported delay minutes.
- 36%Late-arriving aircraft
- 32%Carrier
- 29%National Airspace System
- 3%Extreme weather
36% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 15,000 reported delay minutes here, that single category outweighs weather by 14 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 15,393 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 84.8% on time here.
Cancellations are rare at 0.80%, below the national 1.81% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.
Connections and stage length
What a delay here costs
8.7% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, which a normal layover absorbs.
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 is a different operation and performs like one: it runs 63.7% on time across 879 flights, 5 points below this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 5 points of difference.
One caution: this is a thin sample. 879 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.
What to do with this
Booking Southwest on PHL to DEN
Put together: treat all of this as provisional. 879 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 69.0% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 864 completed flights over 12 months sit behind that.
Related
Where to go next
- PHL to DEN, every carrier
- Southwest on DEN to PHL, the return leg
- United Airlines on PHL to DEN83.9%
- American Airlines on PHL to DEN73.3%
- Frontier Airlines on PHL to DEN68.4%
- Southwest Airlines network-wide record
- Philadelphia International (PHL) delay statistics
- Denver International (DEN) delay statistics
- Same route, different airline: where the carrier you pick matters most
- Why the first flight of the morning is statistically safest
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.