Carrier route record

WNGRR→DEN

Southwest Airlines · Grand Rapids to Denver

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 GRR 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 359 flights, with a median arrival 3 minutes early.

The national on-time rate over the same period is 77.3%, so Southwest on GRR to DEN runs 5 points behind the country as a whole. Across a thousand flights that is about 48 extra late arrivals.

On time

72.5%

Arrivals under 15 minutes late, of 356 completed flights

Avg delay

56 min

Across delayed arrivals only, not all flights

Cancelled

0.28%

National rate is 1.89%

Whole route

76.1%

Every carrier on GRR to DEN, 1,234 flights

These figures cover 359 flights between September 2025 and August 2026. The median arrival is 3 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 GRR to DEN

Southwest flew 359 of the 1,234 flights on GRR to DEN, about 29% of it. Its 72.5% on time is 4 points worse than the route as a whole, which runs 76.1%. 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 72.5%. 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.

On-time performance by carrier on GRR to DEN
Airline	Flights	On time	Avg delay	Cancelled	Grade
SkyWest Airlinesthin sample	1	100.0%	—	0.00%	A+
United Airlines	727	77.6%	81 min	0.55%	B+
Frontier Airlinesthin sample	147	77.2%	107 min	0.00%	B+
Southwest Airlines (this page)thin sample	359	72.5%	56 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 48 points, against half a point between the best and worst carrier.

5am–8am50 flights89.8%
8am–11am113 flights86.7%
11am–2pm43 flights81.4%
2pm–5pm92 flights60.0%
5pm–8pm52 flights42.3%
8pm–5am9 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: 42.3% on time, against 89.8% 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 113 flights scheduled in it.

Across the year

Southwest on GRR to DEN through the year

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

June is the worst month at 29.4% on time, 67 points below October, the best at 96.8%. 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, Sunday is the strongest day at 81.8% on time and Wednesday the weakest at 60.4%, a spread of 21 points.

Arrival by arrival

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

The 98 late arrivals split 43 under half an hour, 29 between 30 and 60 minutes, and 26 an hour or more.

15+ min early64 flights18.0%
Within 15 min194 flights54.5%
15–29 min late43 flights12.1%
30–59 min late29 flights8.1%
1–2 hours late15 flights4.2%
2+ hours late11 flights3.1%

Scale runs 0% to 100%.

Share of 356 completed flights by arrival against schedule.

17 of 89 late departures made up the time and arrived on time, 19% of them. In the other direction, 26 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 GRR to DEN

The latest arrival of the period was on 8 June 2026, 6 hours 8 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. The five worst days are spread across June, January, July and August, with no single month standing out.

The latest arrivals of Southwest on GRR to DEN in the period
Date	Arrived late by	Largest filed cause
8 June 2026	6 hours 8 minutes	Late-arriving aircraft
26 January 2026	4 hours 39 minutes	Carrier
22 July 2026	3 hours 46 minutes	National Airspace System
3 January 2026	3 hours 37 minutes	Late-arriving aircraft
9 August 2026	2 hours 59 minutes	Carrier

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 5,469 reported delay minutes.

Late-arriving aircraft
37%
National Airspace System
36%
Carrier
24%
Extreme weather
2%

37% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 5,469 reported delay minutes here, that single category outweighs weather by 15 to one. The split is drawn from 5,469 reported delay minutes.

36% 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 1,984 minutes out of 5,469, against a national NAS share of 21%.

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 about an hour, 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 69.5% on time across 359 flights, 3 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 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 GRR to DEN

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 72.5% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 356 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