Carrier route record
DLSLC→ONT
Delta Air Lines · Salt Lake City to Ontario
- 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 SLC to ONT 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 10 points better than the national rate of 77.3%. When something does go wrong the average delay runs about an hour. That rests on 869 flights, with a median arrival 8 minutes early.
Set against the rest of the country, Delta's SLC to ONT record is 10 points better than the US average of 77.3%. That gap is worth roughly 98 fewer late arrivals for every thousand flights.
Key figures
On time
87.1%
Arrivals under 15 minutes late, of 860 completed flights
Avg delay
60 min
Across delayed arrivals only, not all flights
Cancelled
1.04%
National rate is 1.89%
Whole route
88.9%
Every carrier on SLC to ONT, 1,239 flights
These figures cover 869 flights between September 2025 and August 2026. The median arrival is 8 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 SLC to ONT
Delta flew 869 of the 1,239 flights on SLC to ONT, most of the route. Its 87.1% on time is 2 points worse than the route as a whole, which runs 88.9%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from SkyWest at 93.2% to Delta at 87.1%. 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 | 93.2% | 62 min | 0.29% | A+ |
| Frontier Airlinesthin sample | 30 | 93.1% | 101 min | 3.33% | A− |
| Delta Air Lines (this page) | 869 | 87.1% | 60 min | 1.04% | A |
Flight by flight
Delta flight numbers on SLC to ONT
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 matters more here than the choice of carrier. The gap between the best and worst window is 11 points, against half a point between the best and worst carrier.
- 5am–8am—
- 8am–11am102 flights94.1%
- 11am–2pm342 flights84.3%
- 2pm–5pm60 flights82.8%
- 5pm–8pm1 flights—
- 8pm–5am364 flights88.4%
Scale runs 75% to 100%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 94.1% of the time, against 82.8% for the afternoon window. That is 11 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8pm–5am window is the busiest, with 364 flights scheduled in it.
Across the year
Delta on SLC to ONT through the year
February is the weak month at 79.5% on time, against 93.8% in May. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. July was the busiest month here, with 85 flights.
Across the week, Tuesday is the strongest day at 90.5% on time and Saturday the weakest at 79.2%, a spread of 11 points.
Arrival by arrival
How late Delta on SLC to ONT runs when it is late
Delta on SLC to ONT often beats the schedule: 256 of 860 completed flights, 30%, arrived 15 minutes or more early. The 111 late arrivals split 50 under half an hour, 25 between 30 and 60 minutes, and 36 an hour or more.
- 15+ min early256 flights29.8%
- Within 15 min493 flights57.3%
- 15–29 min late50 flights5.8%
- 30–59 min late25 flights2.9%
- 1–2 hours late22 flights2.6%
- 2+ hours late14 flights1.6%
Scale runs 0% to 100%.
Share of 860 completed flights by arrival against schedule.
27 of 116 late departures made up the time and arrived on time, 23% of them. 22 flights left on time and still arrived late.
The worst days
Worst days for Delta on SLC to ONT
The latest arrival of the period was on 17 July 2026, 8 hours 46 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on three of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 17 July 2026 | 8 hours 46 minutes | Carrier |
| 18 August 2026 | 7 hours 56 minutes | Carrier |
| 18 February 2026 | 4 hours 16 minutes | Extreme weather |
| 14 September 2025 | 3 hours | Carrier |
| 15 January 2026 | 2 hours 59 minutes | Late-arriving aircraft |
Delay causes
Why Delta runs late on this route
Carrier accounts for 64% of the 6,709 delay minutes carriers reported here, and the remaining four split what is left.
- 64%Carrier
- 21%Late-arriving aircraft
- 10%National Airspace System
- 6%Extreme weather
The largest share of delay minutes, 64%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 4,269 of the 6,709 delay minutes reported here. The split is drawn from 6,709 reported delay minutes.
Cancellations sit at 1.04% against a national 1.89%, which is ordinary. Diversions add another 0.00%.
Connections and stage length
What a delay here costs
Badly late arrivals are rare here: only 4.2% 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 91.1% on time across 869 flights, 4 points above 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 SLC to ONT
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 87.1% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 860 completed flights over 12 months sit behind that.
Related
Where to go next
- SLC to ONT, every carrier
- Delta on ONT to SLC, the return leg
- SkyWest Airlines on SLC to ONT93.2%
- Delta Air Lines network-wide record
- Salt Lake City International (SLC) delay statistics
- Ontario International (ONT) delay statistics
- The best time of day to fly, according to 7.05 million flight records
- Worst months to fly in the US, ranked by the data
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.