Carrier route record
WNDEN→BHM
Southwest Airlines · Denver to Birmingham
- Flights
- 509
- Period
- September 2025 to August 2026
- Share of route
- 41%
- Carriers
- 3
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on DEN to BHM draws a D+. Roughly one flight in three arrives at least 15 minutes late, and the typical late arrival is about an hour behind schedule. Build slack into anything you connect to. That rests on 509 flights, with a median arrival 6 minutes late.
The national on-time rate over the same period is 77.3%, so Southwest on DEN to BHM runs 14 points behind the country as a whole. Across a thousand flights that is about 140 extra late arrivals.
Key figures
On time
63.3%
Arrivals under 15 minutes late, of 507 completed flights
Avg delay
63 min
Across delayed arrivals only, not all flights
Cancelled
0.39%
National rate is 1.89%
Whole route
72.5%
Every carrier on DEN to BHM, 1,236 flights
These figures cover 509 flights between September 2025 and August 2026. Beyond the headline rate, 13.4% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Southwest against every carrier on DEN to BHM
Southwest flew 509 of the 1,236 flights on DEN to BHM, about 41% of it. Its 63.3% on time is 9 points worse than the route as a whole, which runs 72.5%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from SkyWest at 79.2% to Southwest at 63.3%. 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 | 604 | 79.2% | 78 min | 0.33% | B+ |
| United Airlinesthin sample | 123 | 77.2% | 56 min | 0.00% | B+ |
| Southwest Airlines (this page) | 509 | 63.3% | 63 min | 0.39% | D+ |
Timetable by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
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 23 points, against half a point between the best and worst carrier.
- 5am–8am—
- 8am–11am100 flights76.8%
- 11am–2pm79 flights73.4%
- 2pm–5pm51 flights70.6%
- 5pm–8pm184 flights53.6%
- 8pm–5am95 flights55.8%
Scale runs 45% to 80%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 53.6% on time, against 76.8% 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 184 flights scheduled in it.
Across the year
Southwest on DEN to BHM through the year
August is the worst month at 34.7% on time, 46 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. July was the busiest month here, with 58 flights.
Across the week, Tuesday is the strongest day at 72.7% on time and Thursday the weakest at 56.2%, a spread of 17 points.
Arrival by arrival
How late Southwest on DEN to BHM runs when it is late
The 186 late arrivals split 61 under half an hour, 57 between 30 and 60 minutes, and 68 an hour or more.
- 15+ min early41 flights8.1%
- Within 15 min280 flights55.2%
- 15–29 min late61 flights12.0%
- 30–59 min late57 flights11.2%
- 1–2 hours late42 flights8.3%
- 2+ hours late26 flights5.1%
Scale runs 0% to 100%.
Share of 507 completed flights by arrival against schedule.
42 of 209 late departures made up the time and arrived on time, 20% of them. 19 flights left on time and still arrived late.
The worst days
Worst days for Southwest on DEN to BHM
The latest arrival of the period was on 13 August 2026, 6 hours 40 minutes behind schedule; most of its delay minutes were filed as extreme weather. Four of the five worst days fell in August 2026.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 13 August 2026 | 6 hours 40 minutes | Extreme weather |
| 6 August 2026 | 5 hours 49 minutes | Late-arriving aircraft |
| 22 July 2026 | 4 hours 33 minutes | Late-arriving aircraft |
| 24 August 2026 | 4 hours 19 minutes | Late-arriving aircraft |
| 21 August 2026 | 4 hours 17 minutes | Late-arriving aircraft |
Delay causes
Why Southwest runs late on this route
Late-arriving aircraft accounts for 65% of the 12,000 delay minutes carriers reported here, and the remaining four split what is left.
- 65%Late-arriving aircraft
- 23%Carrier
- 9%National Airspace System
- 3%Extreme weather
65% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 12,000 reported delay minutes here, that single category outweighs weather by 23 to one. The split is drawn from 11,661 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 76.8% on time here.
Cancellations are rare at 0.39%, below the national 1.89% 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
13.4% 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.
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.
The return leg is a different operation and performs like one: it runs 77.8% on time across 509 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. 509 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. 509 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 63.3% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 507 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 BHM79.2%
- United Airlines on DEN to BHM77.2%
- 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 7.05 million flight records
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.