Carrier route record
WNDEN→ATL
Southwest Airlines · Denver to Atlanta
- Flights
- 1,080
- Period
- July 2025 to June 2026
- Share of route
- 19%
- Carriers
- 4
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on DEN to ATL draws a C+. 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 1,080 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 2,805 at 86.3% on time.
Delta Air Lines is the most reliable of the three carriers covered here at 86.3% on time across 2,805 flights.
Key figures
On time
66.3%
Arrivals under 15 minutes late, of 1,067 completed flights
Avg delay
54 min
Across delayed arrivals only, not all flights
Cancelled
0.83%
National rate is 1.81%
Whole route
80.0%
Every carrier on DEN to ATL, 5,596 flights
These figures cover 1,080 flights between July 2025 and June 2026. Beyond the headline rate, 9.4% 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 ATL
Southwest flew 1,080 of the 5,596 flights on DEN to ATL, about 19% of it. Its 66.3% on time is 14 points worse than the route as a whole, which runs 80.0%. Ranked by on-time rate it is last of four carriers on the route, where the range runs from Delta at 86.3% to Southwest at 66.3%.
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 86.3% of the time; United Airlines manages 78.0%. Sample sizes sit next to every figure, because a two-point gap across 967 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines | 2,805 | 86.3% | 71 min | 1.07% | A |
| Frontier Airlines | 744 | 78.9% | 61 min | 0.81% | B+ |
| United Airlines | 967 | 78.0% | 64 min | 0.31% | B+ |
| Southwest Airlines (this page) | 1,080 | 66.3% | 54 min | 0.83% | C+ |
Delta leads United by 8 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 46 points, against 8 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am66 flights95.4%
- 8am–11am310 flights79.5%
- 11am–2pm148 flights76.9%
- 2pm–5pm267 flights55.9%
- 5pm–8pm227 flights49.3%
- 8pm–5am62 flights50.0%
Scale runs 40% to 100%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 49.3% on time, against 95.4% 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 310 flights scheduled in it.
Across the year
Southwest on DEN to ATL through the year
June is the worst month at 41.7% on time, 48 points below November, the best at 89.2%. 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. January was the busiest month here, with 93 flights.
Across the week, Tuesday is the strongest day at 74.2% on time and Sunday the weakest at 57.6%. 17 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 47% of the 19,000 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.
- 47%Late-arriving aircraft
- 39%Carrier
- 12%National Airspace System
- 2%Extreme weather
- 1%Security
47% 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 19,000 reported delay minutes here, that single category outweighs weather by 26 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 19,293 reported delay minutes.
The largest share of delay minutes, 39%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 7,428 of the 19,000 delay minutes reported here.
Cancellations are rare at 0.83%, 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. 9.4% 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 1,199 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 73.4% on time across 1,079 flights, 7 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 7 points of difference.
One caution: this is a thin sample. 1,080 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 ATL
Put together: treat all of this as provisional. 1,080 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 66.3% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 1,067 completed flights over 12 months sit behind that.
Related
Where to go next
- DEN to ATL, every carrier
- Southwest on ATL to DEN, the return leg
- Delta Air Lines on DEN to ATL86.3%
- Frontier Airlines on DEN to ATL78.9%
- United Airlines on DEN to ATL78.0%
- Southwest Airlines network-wide record
- Denver International (DEN) delay statistics
- Hartsfield-Jackson Atlanta International (ATL) 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.