Route reliability record
DEN→SLC
Denver to Salt Lake City
- Flights
- 7,713
- Period
- September 2025 to August 2026
- Distance
- 391 mi
- Carriers
- 5
This route lands a B+, about a point better than the national rate of 77.3%. Roughly one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 7,713 DEN to SLC flights, of which Delta Air Lines flew 1,698 at 82.0% on time.
Best time to fly DEN to SLC: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 91.2% of the time and Tuesday flights 83.6%, against 78.2% for the route overall.
Delta Air Lines is the most reliable of the five carriers covered here at 82.0% on time across 1,698 flights.
Key figures
On time
78.2%
Arrivals under 15 minutes late, of 7,676 completed flights
Avg delay
61 min
Across delayed arrivals only, not all flights
Cancelled
0.35%
National rate is 1.89%
Best carrier
Delta
82.0% on time across 1,698 flights
These figures cover 7,713 flights between September 2025 and August 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.
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Carrier by carrier
Which airline is most reliable on DEN to SLC
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 82.0% of the time; Southwest Airlines manages 72.1%. Sample sizes sit next to every figure, because a two-point gap across 2,280 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines | 1,698 | 82.0% | 78 min | 0.35% | B+ |
| Frontier Airlines | 1,033 | 81.9% | 57 min | 0.29% | B+ |
| SkyWest Airlines | 1,386 | 80.2% | 66 min | 0.58% | B+ |
| United Airlines | 1,316 | 79.0% | 57 min | 0.15% | B+ |
| Southwest Airlines | 2,280 | 72.1% | 53 min | 0.35% | C+ |
Delta leads Southwest by 10 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
Flight by flight
Flights on DEN to SLC
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 Denver to Salt Lake City
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. DEN → SLCDenver to Salt Lake City | Delta Air Lines | 81.7% | 82.0% | 0.35% | 5am–8am, Tue | DL 1581 07:05 |
| 2. DEN → SLCDenver to Salt Lake City | Frontier Airlines | 81.7% | 81.9% | 0.29% | 5am–8am, Tue | F9 4251 22:29 |
| 3. DEN → SLCDenver to Salt Lake City | SkyWest Airlines | 79.7% | 80.2% | 0.58% | 11am–2pm, Tue | OO 5762 17:45 |
| 4. DEN → SLCDenver to Salt Lake City | United Airlines | 78.9% | 79.0% | 0.15% | 8am–11am, Tue | UA 1963 11:45 |
| 5. DEN → SLCDenver to Salt Lake City | Southwest Airlines | 71.8% | 72.1% | 0.35% | 8am–11am, Tue | — |
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 24 points, against 10 points between the best and worst carrier.
- 5am–8am897 flights91.2%
- 8am–11am1,267 flights87.5%
- 11am–2pm1,530 flights80.9%
- 2pm–5pm1,404 flights77.8%
- 5pm–8pm1,454 flights67.0%
- 8pm–5am1,161 flights69.1%
Scale runs 60% to 95%.
Book the early departure. Flights leaving between 5am–8am arrive on time 91.2% of the time, against 67.0% for the evening window. That is 24 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 11am–2pm window is the busiest, with 1,530 flights scheduled in it.
Explore
Filter DEN to SLC 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 DEN to SLC, the best departure window is 5am–8am at 91.2% on time and the worst is 5pm–8pm at 67.0%, a wide gap of 24.2 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am91.2%
- 8–11am87.5%
- 11am–2pm80.9%
- 2–5pm77.8%
- 5–8pm67.0%
- 8pm–5am69.1%
best all US flightsScale 60% to 95%.
Across the year
When delays peak on this route
This route's year swings by 17 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 66.8% on time, 17 points below February, the best at 84.1%. 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 668 flights.
Across the week, Tuesday is the strongest day at 83.6% on time and Sunday the weakest at 74.5%, a spread of 9 points.
Delay causes
Why this route gets delayed
Late-arriving aircraft accounts for 45% of the 101,000 delay minutes carriers reported here, and the remaining four split what is left.
- 45%Late-arriving aircraft
- 37%Carrier
- 13%National Airspace System
- 4%Extreme weather
- 0%Security
45% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 101,000 reported delay minutes here, that single category outweighs weather by 11 to one. The split is drawn from 101,402 reported delay minutes.
The largest share of delay minutes, 37%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 38,000 of the 101,000 delay minutes reported here.
Cancellations are rare at 0.35%, 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
6.6% 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 79.0% on time across 7,709 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 7,713 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 SLC 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. February runs 84.1% on time and August 66.8%, a swing of 17 points. If the dates move at all, move them out of August before you think about anything else. 7,676 completed flights over 12 months sit behind that.
Common questions
DEN to SLC questions
How often is DEN to SLC delayed?
Roughly 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 21.8% of the 7,713 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on DEN to SLC?
Delta Air Lines leads at 82.0% on time across 1,698 flights. Southwest Airlines is at the other end on 72.1%, a gap of 10 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 DEN to SLC?
The 5am–8am departure window is the strongest at 91.2% on time. The 5pm–8pm window is the weakest at 67.0%, 24 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 DEN to SLC?
August is the weakest month at 66.8% on time, compared with 84.1% in February. Across the year that is 17 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
- SLC to DEN — the return legseparate record
- Denver International (DEN) delay statistics
- Salt Lake City International (SLC) delay statistics
- Delta Air Lines on DEN to SLC82.0%
- Frontier Airlines on DEN to SLC81.9%
- SkyWest Airlines on DEN to SLC80.2%
- United Airlines on DEN to SLC79.0%
- Southwest Airlines on DEN to SLC72.1%
- DEN to PHX, a related route75.6%
- PHX to SLC, a related route83.0%
- DEN to LAX, a related route78.7%
- Delta Air Lines on-time record82.0%
- Frontier Airlines on-time record81.9%
- SkyWest Airlines on-time record80.2%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
Direction matters. DEN to SLC and SLC to DEN 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.