Carrier route record
DLONT→SLC
Delta Air Lines · Ontario to Salt Lake City
- Flights
- 869
- Period
- September 2025 to August 2026
- Share of route
- 70%
- Carriers
- 3
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Delta Air Lines.
Delta on ONT to SLC earns an A. Close to nine flights in ten arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 14 points better than the national rate of 77.3%. When something does go wrong the average delay runs an hour and a half. That rests on 869 flights, with a median arrival 14 minutes early.
Set against the rest of the country, Delta's ONT to SLC record is 14 points better than the US average of 77.3%. That gap is worth roughly 138 fewer late arrivals for every thousand flights.
Key figures
On time
91.1%
Arrivals under 15 minutes late, of 858 completed flights
Avg delay
84 min
Across delayed arrivals only, not all flights
Cancelled
1.15%
National rate is 1.89%
Whole route
91.1%
Every carrier on ONT to SLC, 1,239 flights
These figures cover 869 flights between September 2025 and August 2026. The median arrival is 14 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
Delta against every carrier on ONT to SLC
Delta flew 869 of the 1,239 flights on ONT to SLC, most of the route. Its 91.1% on time is about level with the route as a whole at 91.1%. Ranked by on-time rate it is number two of three carriers on the route, where the range runs from SkyWest at 91.4% to Frontier at 86.7%. 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 | 340 | 91.4% | 99 min | 0.29% | A+ |
| Delta Air Lines (this page) | 869 | 91.1% | 84 min | 1.15% | A |
| Frontier Airlinesthin sample | 30 | 86.7% | 42 min | 0.00% | A+ |
Flight by flight
Delta flight numbers on ONT to SLC
Timetable by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
Departure window
When Delta runs best on this route
Departure time is the single lever a traveller controls, and it moves the odds more than most people expect. Each bar below is the on-time rate for flights scheduled to leave inside that window, across 869 flights.
- 5am–8am365 flights94.5%
- 8am–11am95 flights95.7%
- 11am–2pm349 flights87.2%
- 2pm–5pm—
- 5pm–8pm60 flights86.2%
- 8pm–5am—
Scale runs 80% to 100%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 95.7% of the time, against 86.2% for the evening window. That is 10 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5am–8am window is the busiest, with 365 flights scheduled in it.
Across the year
Delta on ONT to SLC through the year
August is the worst month at 85.5% on time, 11 points below June, the best at 96.4%. 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 85 flights.
Across the week, Tuesday is the strongest day at 94.4% on time and Thursday the weakest at 86.5%, a spread of 8 points.
Arrival by arrival
How late Delta on ONT to SLC runs when it is late
Delta on ONT to SLC often beats the schedule: 392 of 858 completed flights, 46%, arrived 15 minutes or more early. The 76 late arrivals split 20 under half an hour, 21 between 30 and 60 minutes, and 35 an hour or more.
- 15+ min early392 flights45.7%
- Within 15 min390 flights45.5%
- 15–29 min late20 flights2.3%
- 30–59 min late21 flights2.4%
- 1–2 hours late17 flights2.0%
- 2+ hours late18 flights2.1%
Scale runs 0% to 100%.
Share of 858 completed flights by arrival against schedule.
21 of 91 late departures made up the time and arrived on time, 23% of them. Only 6 left on time and still arrived late.
The worst days
Worst days for Delta on ONT to SLC
The latest arrival of the period was on 2 September 2025, 7 hours 54 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). Three of the five worst days fell in February 2026.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 2 September 2025 | 7 hours 54 minutes | Carrier |
| 13 February 2026 | 6 hours 59 minutes | Carrier |
| 7 December 2025 | 5 hours 32 minutes | Carrier |
| 6 February 2026 | 4 hours 11 minutes | Carrier |
| 18 February 2026 | 3 hours 35 minutes | Late-arriving aircraft |
Delay causes
Why Delta runs late on this route
Carrier accounts for 50% of the 6,375 delay minutes carriers reported here, and the remaining four split what is left.
- 50%Carrier
- 46%Late-arriving aircraft
- 4%National Airspace System
- 0%Extreme weather
46% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 6,375 reported delay minutes here, that single category outweighs weather by 46 to one. The split is drawn from 6,375 reported delay minutes.
The largest share of delay minutes, 50%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 3,160 of the 6,375 delay minutes reported here.
Cancellations sit at 1.15% against a national 1.89%, which is ordinary. Diversions add another 0.12%.
Connections and stage length
What a delay here costs
Badly late arrivals are rare here: only 4.1% land an hour or more behind schedule, against 8.3% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.
The 558 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 87.1% on time across 869 flights, 4 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 4 points of difference.
One caution: this is a thin sample. 869 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 Delta on ONT to SLC
Put together: treat all of this as provisional. 869 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 91.1% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 858 completed flights over 12 months sit behind that.
Related
Where to go next
- ONT to SLC, every carrier
- Delta on SLC to ONT, the return leg
- SkyWest Airlines on ONT to SLC91.4%
- Delta Air Lines network-wide record
- Ontario International (ONT) delay statistics
- Salt Lake City International (SLC) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
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.