Carrier route record

WNMEM→DEN

Southwest Airlines · Memphis to Denver

Flights: 522
Period: September 2025 to August 2026
Share of route: 37%
Carriers: 4

Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Southwest Airlines.

Southwest on MEM 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, 5 points worse than the national rate of 77.3%. The late ones land about an hour behind schedule. That rests on 522 flights, with a median arrival 4 minutes early.

The national on-time rate over the same period is 77.3%, so Southwest on MEM to DEN runs 5 points behind the country as a whole. Across a thousand flights that is about 45 extra late arrivals.

On time

72.8%

Arrivals under 15 minutes late, of 518 completed flights

Avg delay

58 min

Across delayed arrivals only, not all flights

Cancelled

0.57%

National rate is 1.89%

Whole route

77.7%

Every carrier on MEM to DEN, 1,395 flights

These figures cover 522 flights between September 2025 and August 2026. The median arrival is 4 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.

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Carrier by carrier

Southwest against every carrier on MEM to DEN

Southwest flew 522 of the 1,395 flights on MEM to DEN, about 37% of it. Its 72.8% on time is 5 points worse than the route as a whole, which runs 77.7%. 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 72.8%. 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.

On-time performance by carrier on MEM to DEN
Airline	Flights	On time	Avg delay	Cancelled	Grade
SkyWest Airlinesthin sample	1	100.0%	—	0.00%	A+
United Airlines	727	81.6%	81 min	0.96%	B+
Frontier Airlinesthin sample	145	75.5%	89 min	0.69%	B+
Southwest Airlines (this page)	522	72.8%	58 min	0.57%	C+

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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 48 points, against half a point between the best and worst carrier.

5am–8am176 flights90.2%
8am–11am142 flights85.7%
11am–2pm29 flights—
2pm–5pm5 flights—
5pm–8pm165 flights42.4%
8pm–5am5 flights—

Scale runs 35% to 95%. Rows with fewer than 30 flights show a dash.

The 5pm–8pm window is where this operation falls apart: 42.4% on time, against 90.2% 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 176 flights scheduled in it.

Across the year

Southwest on MEM to DEN through the year

Darker means more delays. Figures are on-time percentages.January best, June worst

June is the worst month at 50.0% on time, 37 points below January, the best at 86.7%. 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. August was the busiest month here, with 61 flights.

The day of the week is close to irrelevant here: 4 points separates the best day from the worst. Weekly demand peaks are not what drives the delays on this operation.

Arrival by arrival

How late Southwest on MEM to DEN runs when it is late

The 141 late arrivals split 56 under half an hour, 44 between 30 and 60 minutes, and 41 an hour or more.

15+ min early69 flights13.3%
Within 15 min308 flights59.5%
15–29 min late56 flights10.8%
30–59 min late44 flights8.5%
1–2 hours late24 flights4.6%
2+ hours late17 flights3.3%

Scale runs 0% to 100%.

Share of 518 completed flights by arrival against schedule.

23 of 136 late departures made up the time and arrived on time, 17% of them. In the other direction, 28 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at DEN.

The worst days

Worst days for Southwest on MEM to DEN

The latest arrival of the period was on 4 December 2025, 5 hours behind schedule; most of its delay minutes were filed as a late-arriving aircraft. Three of the five worst days fell in March 2026.

The latest arrivals of Southwest on MEM to DEN in the period
Date	Arrived late by	Largest filed cause
4 December 2025	5 hours	Late-arriving aircraft
19 May 2026	4 hours 37 minutes	Carrier
13 March 2026	4 hours	Late-arriving aircraft
7 March 2026	3 hours 53 minutes	National Airspace System
11 March 2026	3 hours 23 minutes	Late-arriving aircraft

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 8,218 reported delay minutes.

National Airspace System
40%
Late-arriving aircraft
39%
Carrier
20%
Extreme weather
1%
Security
0%

39% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 8,218 reported delay minutes here, that single category outweighs weather by 39 to one. The split is drawn from 8,218 reported delay minutes.

40% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 3,282 minutes out of 8,218, against a national NAS share of 21%.

Cancellations are rare at 0.57%, 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

7.9% of arrivals land an hour or more late, close to the national 8.3%, so 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.

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.

The return leg is a different operation and performs like one: it runs 64.9% on time across 522 flights, 8 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 8 points of difference.

One caution: this is a thin sample. 522 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 MEM to DEN

Put together: treat all of this as provisional. 522 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 72.8% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 518 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated 22 October 2026; recomputed monthly. How this data is collected.

Key figures