Carrier route record
WNDEN→GRR
Southwest Airlines · Denver to Grand Rapids
- Flights
- 359
- Period
- September 2025 to August 2026
- Share of route
- 29%
- Carriers
- 4
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on DEN to GRR sits in the middle of the pack with a C+. About seven flights in ten arrive on time by the DOT's definition, 8 points worse than the national rate of 77.3%. The late ones land roughly 45 minutes behind schedule. That rests on 359 flights, with a median arrival 5 minutes late.
The national on-time rate over the same period is 77.3%, so Southwest on DEN to GRR runs 8 points behind the country as a whole. Across a thousand flights that is about 78 extra late arrivals.
Key figures
On time
69.5%
Arrivals under 15 minutes late, of 357 completed flights
Avg delay
43 min
Across delayed arrivals only, not all flights
Cancelled
0.28%
National rate is 1.89%
Whole route
76.5%
Every carrier on DEN to GRR, 1,235 flights
These figures cover 359 flights between September 2025 and August 2026. On-time means an arrival less than 15 minutes after the scheduled gate time, the same threshold the Department of Transportation uses in its own reports. Cancelled and diverted flights are excluded from the on-time rate and counted separately, which is why the cancellation column matters on its own.
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Carrier by carrier
Southwest against every carrier on DEN to GRR
Southwest flew 359 of the 1,235 flights on DEN to GRR, about 29% of it. Its 69.5% on time is 7 points worse than the route as a whole, which runs 76.5%. 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 69.5%. 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 | 148 | 85.1% | 72 min | 0.00% | A+ |
| United Airlines | 727 | 78.3% | 56 min | 0.28% | B+ |
| Southwest Airlines (this page)thin sample | 359 | 69.5% | 43 min | 0.28% | 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 34 points, against half a point between the best and worst carrier.
- 5am–8am—
- 8am–11am31 flights77.4%
- 11am–2pm131 flights71.0%
- 2pm–5pm84 flights86.7%
- 5pm–8pm112 flights53.2%
- 8pm–5am1 flights—
Scale runs 45% to 90%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 53.2% on time, against 86.7% 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 11am–2pm window is the busiest, with 131 flights scheduled in it.
Across the year
Southwest on DEN to GRR through the year
June is the worst month at 50.0% on time, 34 points below January, the best at 83.9%. 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 36 flights.
Across the week, Tuesday is the strongest day at 83.0% on time and Wednesday the weakest at 58.3%, a spread of 25 points.
Arrival by arrival
How late Southwest on DEN to GRR runs when it is late
The 109 late arrivals split 49 under half an hour, 34 between 30 and 60 minutes, and 26 an hour or more.
- 15+ min early27 flights7.6%
- Within 15 min221 flights61.9%
- 15–29 min late49 flights13.7%
- 30–59 min late34 flights9.5%
- 1–2 hours late22 flights6.2%
- 2+ hours late4 flights1.1%
Scale runs 0% to 100%.
Share of 357 completed flights by arrival against schedule.
36 of 133 late departures made up the time and arrived on time, 27% of them. 12 flights left on time and still arrived late.
The worst days
Worst days for Southwest on DEN to GRR
The latest arrival of the period was on 22 September 2025, 2 hours 54 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. On three of the five worst days the largest share was filed as carrier-caused (crew, maintenance, fuelling, baggage).
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 22 September 2025 | 2 hours 54 minutes | Late-arriving aircraft |
| 28 November 2025 | 2 hours 42 minutes | Carrier |
| 25 February 2026 | 2 hours 22 minutes | Carrier |
| 30 November 2025 | 2 hours 8 minutes | Carrier |
| 5 October 2025 | 1 hour 48 minutes | Late-arriving aircraft |
Delay causes
Why Southwest runs late on this route
Late-arriving aircraft accounts for 45% of the 4,702 delay minutes carriers reported here, and the remaining four split what is left.
- 45%Late-arriving aircraft
- 43%Carrier
- 12%National Airspace System
45% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 4,702 reported delay minutes here, that single category outweighs weather by 45 to one. The split is drawn from 4,702 reported delay minutes.
The largest share of delay minutes, 43%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 2,027 of the 4,702 delay minutes reported here.
Cancellations are rare at 0.28%, 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
7.3% 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 roughly 45 minutes, which a normal layover absorbs.
The 1,015 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 72.5% on time across 359 flights, 3 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 3 points of difference.
One caution: this is a thin sample. 359 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 GRR
Put together: treat all of this as provisional. 359 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 69.5% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 357 completed flights over 12 months sit behind that.
Related
Where to go next
- DEN to GRR, every carrier
- Southwest on GRR to DEN, the return leg
- Frontier Airlines on DEN to GRR85.1%
- United Airlines on DEN to GRR78.3%
- 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 7.05 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.