Route reliability record
SLC→DEN
Salt Lake City to Denver
- Flights
- 7,709
- Period
- September 2025 to August 2026
- Distance
- 391 mi
- Carriers
- 5
This route lands a B+, 2 points better than the national rate of 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 7,709 SLC to DEN flights, of which SkyWest Airlines flew 1,378 at 85.7% on time.
Best time to fly SLC to DEN: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 92.6% of the time and Saturday flights 83.0%, against 79.0% for the route overall.
SkyWest Airlines is the most reliable of the five carriers covered here at 85.7% on time across 1,378 flights.
Key figures
On time
79.0%
Arrivals under 15 minutes late, of 7,647 completed flights
Avg delay
61 min
Across delayed arrivals only, not all flights
Cancelled
0.51%
National rate is 1.89%
Best carrier
SkyWest
85.7% on time across 1,378 flights
These figures cover 7,709 flights between September 2025 and August 2026. The median arrival is 7 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
Which airline is most reliable on SLC to DEN
The choice of carrier is not cosmetic here. SkyWest Airlines arrives on time 85.7% of the time; Southwest Airlines manages 72.4%. Sample sizes sit next to every figure, because a two-point gap across 2,283 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| SkyWest Airlines | 1,378 | 85.7% | 65 min | 0.58% | A+ |
| United Airlines | 1,318 | 82.0% | 69 min | 0.46% | B+ |
| Delta Air Lines | 1,697 | 79.8% | 64 min | 0.18% | B+ |
| Frontier Airlines | 1,033 | 79.3% | 79 min | 0.87% | B+ |
| Southwest Airlines | 2,283 | 72.4% | 49 min | 0.57% | C+ |
The spread between SkyWest and Southwest is 13 points, wide enough that it should decide the booking. On a hundred trips that is 13 more arrivals inside the on-time window.
Flight by flight
Flights on SLC to DEN
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
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Best ways to make this trip
The most reliable ways to fly Salt Lake City to Denver
Every airline on this route, ranked by how often a scheduled flight actually operated and arrived on time, with its best departure time and most punctual flight number. No nearby airport pair beat these.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. SLC → DENSalt Lake City to Denver | SkyWest Airlines | 85.2% | 85.7% | 0.58% | 5am–8am, Wed | OO 5683 05:00 |
| 2. SLC → DENSalt Lake City to Denver | United Airlines | 81.6% | 82.0% | 0.46% | 5am–8am, Tue | — |
| 3. SLC → DENSalt Lake City to Denver | Delta Air Lines | 79.7% | 79.8% | 0.18% | 5am–8am, Tue | DL 1623 13:20 |
| 4. SLC → DENSalt Lake City to Denver | Frontier Airlines | 78.6% | 79.3% | 0.87% | 5am–8am, Sat | F9 3862 08:16 |
| 5. SLC → DENSalt Lake City to Denver | Southwest Airlines | 72.0% | 72.4% | 0.57% | 5am–8am, Sat | — |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
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 26 points, against 13 points between the best and worst carrier.
- 5am–8am1,538 flights92.6%
- 8am–11am1,756 flights77.9%
- 11am–2pm1,360 flights84.3%
- 2pm–5pm1,231 flights66.3%
- 5pm–8pm1,151 flights71.1%
- 8pm–5am673 flights76.2%
Scale runs 60% to 100%.
Book the early departure. Flights leaving between 5am–8am arrive on time 92.6% of the time, against 66.3% for the afternoon window. That is 26 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 1,756 flights scheduled in it.
Explore
Filter SLC to DEN by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On SLC to DEN, the best departure window is 5am–8am at 92.6% on time and the worst is 2pm–5pm at 66.3%, a wide gap of 26.3 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am92.6%
- 8–11am77.9%
- 11am–2pm84.3%
- 2–5pm66.3%
- 5–8pm71.1%
- 8pm–5am76.2%
best all US flightsScale 60% to 95%.
Across the year
When delays peak on this route
This route's year swings by 14 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.
August is the worst month at 70.1% on time, 14 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. March was the busiest month here, with 672 flights.
Across the week, Saturday is the strongest day at 83.0% on time and Friday the weakest at 75.0%, a spread of 8 points.
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 98,000 reported delay minutes.
- 35%National Airspace System
- 31%Carrier
- 31%Late-arriving aircraft
- 2%Extreme weather
- 0%Security
35% 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 34,000 minutes out of 98,000, against a national NAS share of 21%. The split is drawn from 97,733 reported delay minutes.
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 92.6% on time here.
Cancellations are rare at 0.51%, 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 actually costs
6.3% 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.
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 78.2% on time across 7,713 flights, within about 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 7,709 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.
Work out the risk of missing a connection in DEN after this flight
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 August 70.1%, a swing of 14 points. If the dates move at all, move them out of August before you think about anything else. 7,647 completed flights over 12 months sit behind that.
Common questions
SLC to DEN questions
How often is SLC to DEN delayed?
About one flight in five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 21.0% of the 7,709 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on SLC to DEN?
SkyWest Airlines leads at 85.7% on time across 1,378 flights. Southwest Airlines is at the other end on 72.4%, a gap of 13 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 92.6% on time. The 2pm–5pm window is the weakest at 66.3%, 26 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 August delays on SLC to DEN?
August is the weakest month at 70.1% on time, compared with 84.2% in November. Across the year that is 14 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 SLC to DEN85.7%
- United Airlines on SLC to DEN82.0%
- Delta Air Lines on SLC to DEN79.8%
- Frontier Airlines on SLC to DEN79.3%
- Southwest Airlines on SLC to DEN72.4%
- SLC to PHX, a related route83.5%
- PHX to DEN, a related route76.7%
- SLC to LAX, a related route85.6%
- SkyWest Airlines on-time record85.7%
- United Airlines on-time record82.0%
- Delta Air Lines on-time record79.8%
- Same route, different airline: where the carrier you pick matters most
- The best time of day to fly, according to 7.05 million flight records
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.
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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.