Carrier route record
WNDEN→GRR
Southwest Airlines · Denver to Grand Rapids
- Flights
- 363
- Period
- July 2025 to June 2026
- Share of route
- 29%
- 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 GRR draws a C+. About one flight in three arrives at least 15 minutes late, and the typical late arrival is about 45 minutes behind schedule. Build slack into anything you connect to. That rests on 363 flights, with a median arrival 4 minutes late.
The national on-time rate over the same period is 77.6%, so Southwest on DEN to GRR runs 10 points behind the country as a whole. Across a thousand flights that is about 100 extra late arrivals.
Key figures
On time
67.6%
Arrivals under 15 minutes late, of 361 completed flights
Avg delay
45 min
Across delayed arrivals only, not all flights
Cancelled
0.28%
National rate is 1.81%
Whole route
75.3%
Every carrier on DEN to GRR, 1,239 flights
These figures cover 363 flights between July 2025 and June 2026. Beyond the headline rate, 8.9% 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 GRR
Southwest flew 363 of the 1,239 flights on DEN to GRR, about 29% of it. Its 67.6% on time is 8 points worse than the route as a whole, which runs 75.3%. 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 67.6%. 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 | 147 | 87.1% | 74 min | 0.00% | A+ |
| United Airlines | 728 | 76.7% | 54 min | 0.27% | B+ |
| Southwest Airlines (this page)thin sample | 363 | 67.6% | 45 min | 0.28% | 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 36 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–11am25 flights—
- 11am–2pm120 flights68.3%
- 2pm–5pm94 flights86.0%
- 5pm–8pm118 flights50.4%
- 8pm–5am6 flights—
Scale runs 40% to 90%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 50.4% on time, against 86.0% 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 120 flights scheduled in it.
Across the year
Southwest on DEN to GRR through the year
August 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. July was the busiest month here, with 39 flights.
Across the week, Tuesday is the strongest day at 83.3% on time and Thursday the weakest at 57.4%. 26 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 5,285 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
- 13%National Airspace System
- 2%Extreme weather
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 5,285 reported delay minutes here, that single category outweighs weather by 30 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 5,285 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 2,058 of the 5,285 delay minutes reported here.
Cancellations are rare at 0.28%, 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
8.9% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about 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. 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 77.3% on time across 363 flights, 10 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 10 points of difference.
One caution: this is a thin sample. 363 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. 363 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 67.6% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 361 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 GRR87.1%
- United Airlines on DEN to GRR76.7%
- 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.