Carrier route record
DLSLC→ONT
Delta Air Lines · Salt Lake City to Ontario
- Flights
- 902
- Period
- July 2025 to June 2026
- Share of route
- 73%
- Carriers
- 3
Historical statistics for July 2025 to June 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 77.6%. When something does go wrong the average delay runs about an hour. That rests on 902 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 77.6%. That gap is worth roughly 101 fewer late arrivals for every thousand flights.
Key figures
On time
87.7%
Arrivals under 15 minutes late, of 892 completed flights
Avg delay
64 min
Across delayed arrivals only, not all flights
Cancelled
1.11%
National rate is 1.81%
Whole route
89.5%
Every carrier on SLC to ONT, 1,239 flights
These figures cover 902 flights between July 2025 and June 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.
Carrier by carrier
Delta against every carrier on SLC to ONT
Delta flew 902 of the 1,239 flights on SLC to ONT, most of the route. Its 87.7% on time is 2 points worse than the route as a whole, which runs 89.5%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from SkyWest at 94.4% to Delta at 87.7%. 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 | 307 | 94.4% | 52 min | 0.33% | A+ |
| Frontier Airlinesthin sample | 30 | 93.1% | 101 min | 3.33% | A− |
| Delta Air Lines (this page) | 902 | 87.7% | 64 min | 1.11% | A |
Flight by flight
Delta flight numbers on SLC to ONT
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 10 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am—
- 8am–11am130 flights94.5%
- 11am–2pm342 flights85.2%
- 2pm–5pm65 flights84.1%
- 5pm–8pm1 flights—
- 8pm–5am364 flights88.1%
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 94.5% of the time, against 84.1% for the afternoon 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 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. August was the busiest month here, with 93 flights.
Across the week, Friday is the strongest day at 92.5% on time and Saturday the weakest at 85.0%. 8 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Delta runs late on this route
One category carries most of the weight here. Carrier accounts for 61% of the 7,016 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.
- 61%Carrier
- 27%Late-arriving aircraft
- 8%National Airspace System
- 3%Extreme weather
The largest share of delay minutes, 61%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 4,308 of the 7,016 delay minutes reported here. The split is drawn from 7,016 reported delay minutes.
Cancellations sit at 1.11% against a national 1.81%, which is ordinary. Diversions add another 0.00%.
Connections and stage length
What a delay here costs
Badly late arrivals are rare here: only 4.3% land an hour or more behind schedule, against 8.1% 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. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.
The return leg is a different operation and performs like one: it runs 91.7% on time across 902 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. 902 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. 902 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 87.7% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 892 completed flights over 12 months sit behind that.
Related
Where to go next
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.