Carrier route record
WNDEN→BHM
Southwest Airlines · Denver to Birmingham
- Flights
- 464
- Period
- July 2025 to June 2026
- Share of route
- 39%
- Carriers
- 3
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on DEN to BHM draws a D+. About one flight in three arrives at least 15 minutes late, and the typical late arrival is roughly 55 minutes behind schedule. Build slack into anything you connect to. That rests on 464 flights, with a median arrival 5 minutes late.
The national on-time rate over the same period is 77.6%, so Southwest on DEN to BHM runs 13 points behind the country as a whole. Across a thousand flights that is about 130 extra late arrivals.
Key figures
On time
64.6%
Arrivals under 15 minutes late, of 460 completed flights
Avg delay
53 min
Across delayed arrivals only, not all flights
Cancelled
0.86%
National rate is 1.81%
Whole route
73.8%
Every carrier on DEN to BHM, 1,192 flights
These figures cover 464 flights between July 2025 and June 2026. Beyond the headline rate, 10.7% 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 DEN to BHM
Southwest flew 464 of the 1,192 flights on DEN to BHM, about 39% of it. Its 64.6% on time is 9 points worse than the route as a whole, which runs 73.8%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from SkyWest at 80.3% to Southwest at 64.6%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.
Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| SkyWest Airlines | 667 | 80.3% | 66 min | 0.30% | B+ |
| United Airlinesthin sample | 61 | 72.1% | 52 min | 0.00% | C+ |
| Southwest Airlines (this page) | 464 | 64.6% | 53 min | 0.86% | D+ |
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 15 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am—
- 8am–11am76 flights73.3%
- 11am–2pm59 flights72.9%
- 2pm–5pm59 flights66.1%
- 5pm–8pm170 flights60.9%
- 8pm–5am100 flights58.2%
Scale runs 50% to 80%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 58.2% on time, against 73.3% for the 8am–11am 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 5pm–8pm window is the busiest, with 170 flights scheduled in it.
Across the year
Southwest on DEN to BHM through the year
June is the worst month at 48.2% on time, 32 points below January, the best at 80.6%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. April was the busiest month here, with 56 flights.
Across the week, Sunday is the strongest day at 72.1% on time and Thursday the weakest at 57.6%. 14 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Southwest runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 63% of the 8,691 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.
- 63%Late-arriving aircraft
- 27%Carrier
- 10%National Airspace System
63% 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 8,691 reported delay minutes here, that single category outweighs weather by 63 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 8,691 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 73.3% on time here.
Cancellations are rare at 0.86%, 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
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 10.7% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.
The 1,083 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.
The return leg is a different operation and performs like one: it runs 79.1% on time across 464 flights, 15 points above 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 15 points of difference.
One caution: this is a thin sample. 464 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 DEN to BHM
Put together: treat all of this as provisional. 464 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 64.6% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 460 completed flights over 12 months sit behind that.
Related
Where to go next
- DEN to BHM, every carrier
- Southwest on BHM to DEN, the return leg
- SkyWest Airlines on DEN to BHM80.3%
- Southwest Airlines network-wide record
- Denver International (DEN) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
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.