Route reliability record
SLC→DEN
Salt Lake City to Denver
- Flights
- 7,763
- Period
- June 2025 to May 2026
- Distance
- 391 mi
- Carriers
- 5
This route lands a B+, level with the national rate of 77.4%. About one flight in four arrive 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 7,763 flights, of which SkyWest Airlines flew 1,377 at 84.3% on time.
SkyWest Airlines is the most reliable of the five carriers covered here at 84.3% on time across 1,377 flights.
Key figures
On time
76.7%
Arrivals under 15 minutes late, of 7,695 completed flights
Avg delay
62 min
Across delayed arrivals only, not all flights
Cancelled
0.57%
National rate is 1.80%
Best carrier
SkyWest
84.3% on time across 1,377 flights
These figures cover 7,763 flights between June 2025 and May 2026. The median arrival is 6 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.
Carrier by carrier
Which airline is most reliable on SLC to DEN
The choice of carrier is not cosmetic here. SkyWest Airlines arrives on time 84.3% of the time; Southwest Airlines manages 72.0%. Sample sizes sit next to every figure, because a two-point gap across 2,346 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| SkyWest Airlines | 1,377 | 84.3% | 79 min | 0.65% | B+ |
| Delta Air Lines | 1,690 | 77.8% | 63 min | 0.24% | B+ |
| Frontier Airlines | 996 | 77.0% | 70 min | 0.80% | B+ |
| United Airlines | 1,354 | 75.7% | 61 min | 0.52% | B+ |
| Southwest Airlines | 2,346 | 72.0% | 53 min | 0.68% | C+ |
The spread between SkyWest and Southwest is 12 points, wide enough that it should decide the booking. On a hundred trips that is 12 more arrivals inside the on-time window.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 23 points, against 12 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am1,461 flights88.9%
- 8am–11am1,834 flights77.1%
- 11am–2pm1,339 flights83.2%
- 2pm–5pm1,282 flights65.5%
- 5pm–8pm1,186 flights67.6%
- 8pm–5am661 flights73.7%
Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 88.9% of the time, against 65.5% for the afternoon window. That is 23 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on.
Across the year
When delays peak on this route
This route's year swings by 21 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
July is the worst month at 63.5% on time, 21 points below November, the best at 84.2%. 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.
Across the week, Saturday is the strongest day at 82.9% on time and Friday the weakest at 72.2%. 11 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
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 110,000 reported delay minutes.
- 37%National Airspace System
- 32%Carrier
- 29%Late-arriving aircraft
- 2%Extreme weather
- 0%Security
37% 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 41,000 minutes out of 110,000, against a national NAS share of 21%.
The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 88.9% on time here.
Cancellations are rare at 0.57%, below the national 1.80% 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 actually costs
7.2% of arrivals land an hour or more late, close to the national 8.2%. 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 are the about an hour kind, which a normal layover absorbs.
At 391 miles this is a short hop, and stage length matters more than it looks. A flight this short spends under two hours in the air, which leaves almost nothing to claw back a late pushback with. Delay here is decided on the ground, in the turn, which is why the 5am–8am window matters as much as it does.
The return leg runs 77.2% on time across 7,765 flights, within half a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 7,763 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. November runs 84.2% on time and July 63.5%, a swing of 21 points. If the dates move at all, move them out of July before you think about anything else.
Common questions
SLC to DEN questions
How often is SLC to DEN delayed?
About one flight in four arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 23.3% of the 7,763 flights in this analysis, against 22.6% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on SLC to DEN?
SkyWest Airlines leads at 84.3% on time across 1,377 flights. Southwest Airlines is at the other end on 72.0%, a gap of 12 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on SLC to DEN?
The 5am–8am departure window is the strongest at 88.9% on time. The 2pm–5pm window is the weakest at 65.5%, 23 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are July delays on SLC to DEN?
July is the weakest month at 63.5% on time, compared with 84.2% in November. Across the year that is 21 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- DEN to SLC — the return legseparate record
- Salt Lake City International (SLC) delay statistics
- Denver International (DEN) delay statistics
- SkyWest Airlines on-time record84.3%
- Delta Air Lines on-time record77.8%
- Frontier Airlines on-time record77.0%
- The best time of day to fly, according to 7.05 million flight records
- Do budget airlines really get delayed more? The numbers
Direction matters. SLC to DEN and DEN to SLC are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, June 2025 to May 2026. Updated monthly. How this data is collected.