Carrier route record
WNDEN→MEM
Southwest Airlines · Denver to Memphis
- Flights
- 465
- Period
- July 2025 to June 2026
- Share of route
- 35%
- 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 MEM draws a C+. About 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 465 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 MEM runs 12 points behind the country as a whole. Across a thousand flights that is about 123 extra late arrivals.
Key figures
On time
65.3%
Arrivals under 15 minutes late, of 461 completed flights
Avg delay
60 min
Across delayed arrivals only, not all flights
Cancelled
0.86%
National rate is 1.81%
Whole route
75.7%
Every carrier on DEN to MEM, 1,333 flights
These figures cover 465 flights between July 2025 and June 2026. Beyond the headline rate, 11.7% 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 MEM
Southwest flew 465 of the 1,333 flights on DEN to MEM, about 35% of it. Its 65.3% on time is 10 points worse than the route as a whole, which runs 75.7%. Ranked by on-time rate it is last of four carriers on the route, where the range runs from SkyWest at 100.0% to Southwest at 65.3%. Two 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 Airlinesthin sample | 1 | 100.0% | — | 0.00% | A+ |
| Frontier Airlinesthin sample | 139 | 82.6% | 61 min | 0.72% | B+ |
| United Airlines | 728 | 81.0% | 73 min | 0.82% | B+ |
| Southwest Airlines (this page) | 465 | 65.3% | 60 min | 0.86% | C+ |
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 41 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–11am65 flights80.0%
- 11am–2pm91 flights71.1%
- 2pm–5pm80 flights86.2%
- 5pm–8pm160 flights54.1%
- 8pm–5am69 flights44.9%
Scale runs 35% to 90%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 44.9% on time, against 86.2% for the 2pm–5pm 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 160 flights scheduled in it.
Across the year
Southwest on DEN to MEM through the year
July is the worst month at 32.3% on time, 58 points below January, the best at 90.0%. 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, Wednesday is the strongest day at 75.0% on time and Friday the weakest at 55.9%. 19 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 9,548 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
- 30%Carrier
- 7%National Airspace System
- 1%Extreme weather
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 9,548 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 9,548 reported delay minutes.
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. 11.7% 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 872 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 76.3% on time across 465 flights, 11 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 11 points of difference.
One caution: this is a thin sample. 465 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 MEM
Put together: treat all of this as provisional. 465 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 65.3% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 461 completed flights over 12 months sit behind that.
Related
Where to go next
- DEN to MEM, every carrier
- Southwest on MEM to DEN, the return leg
- Frontier Airlines on DEN to MEM82.6%
- United Airlines on DEN to MEM81.0%
- 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.