Route reliability record
ONT→SLC
Ontario to Salt Lake City
- Flights
- 1,239
- Period
- September 2025 to August 2026
- Distance
- 558 mi
- Carriers
- 3
This route 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 1,239 ONT to SLC flights, with a median arrival 14 minutes early.
Best time to fly ONT to SLC: a 8am–11am departure, ideally on a Tuesday. Flights in that window arrived on time 97.4% of the time and Tuesday flights 94.9%, against 91.1% for the route overall.
Set against the rest of the country, this route's 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 1,227 completed flights
Avg delay
86 min
Across delayed arrivals only, not all flights
Cancelled
0.89%
National rate is 1.89%
Best carrier
Delta
91.1% on time across 869 flights
These figures cover 1,239 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
Which airline is most reliable on ONT to SLC
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 | 869 | 91.1% | 84 min | 1.15% | A |
| Frontier Airlinesthin sample | 30 | 86.7% | 42 min | 0.00% | A+ |
Flight by flight
Flights on ONT 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.
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.
Best ways to make this trip
The most reliable ways to fly Ontario to Salt Lake City
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 4 of the top 5 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. LGB → SLCLong Beach to Salt Lake City | SkyWest Airlines | 92.1% | 92.1% | 0.00% | 5am–8am, Mon | OO 3793 16:50 |
| 2. BUR → SLCBurbank to Salt Lake City | Delta Air Lines | 91.2% | 91.9% | 0.71% | 5am–8am, Tue | DL 2582 07:00 |
| 3. BUR → SLCBurbank to Salt Lake City | SkyWest Airlines | 91.2% | 91.7% | 0.53% | 5am–8am, Tue | OO 3693 16:50 |
| 4. ONT → SLCOntario to Salt Lake City | Delta Air Lines | 90.1% | 91.1% | 1.15% | 8am–11am, Tue | DL 2708 06:00 |
| 5. LAX → SLCLos Angeles to Salt Lake City | SkyWest Airlines | 88.0% | 88.0% | 0.00% | 5pm–8pm, 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 11 points, against half a point between the best and worst carrier.
- 5am–8am365 flights94.5%
- 8am–11am154 flights97.4%
- 11am–2pm372 flights86.6%
- 2pm–5pm100 flights91.9%
- 5pm–8pm248 flights88.6%
- 8pm–5am—
Scale runs 80% to 100%. Rows with fewer than 30 flights show a dash.
The weak window here is the middle of the day, not the evening: 11am–2pm runs 86.6% on time against 97.4% for 8am–11am. That shape usually means a departure bank rather than an accumulating delay, so the recovery later in the afternoon is real rather than noise. The 11am–2pm window is the busiest, with 372 flights scheduled in it.
Explore
Filter ONT 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 ONT to SLC, the best departure window is 8am–11am at 97.4% on time and the worst is 11am–2pm at 86.6%, a wide gap of 10.8 points. All US flights leaving 8am–11am ran 83.9%.
- 5–8am94.5%
- 8–11am97.4%
- 11am–2pm86.6%
- 2–5pm91.9%
- 5–8pm88.6%
- 8pm–5am—
best all US flightsScale 60% to 100%. Cells under 30 flights show a dash.
Across the year
When delays peak on this route
Twelve months, one bar each, drawn from the same 1,239 flights. The strip shows how much of this route's record is set by the calendar rather than by the operation.
December is the weak month at 85.6% on time, against 96.5% 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 118 flights.
Across the week, Tuesday is the strongest day at 94.9% on time and Thursday the weakest at 86.4%, a spread of 9 points.
Delay causes
Why this route gets delayed
Carrier accounts for 58% of the 9,397 delay minutes carriers reported here, and the remaining four split what is left.
- 58%Carrier
- 32%Late-arriving aircraft
- 5%Extreme weather
- 4%National Airspace System
The largest share of delay minutes, 58%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 5,489 of the 9,397 delay minutes reported here. The split is drawn from 9,397 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 97.4% on time here.
Cancellations are rare at 0.89%, 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
Badly late arrivals are rare here: only 3.7% 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 runs 88.9% on time across 1,239 flights, within 2 points 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 1,239 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: take the 8am–11am departure, avoid December if the dates are flexible, and if two carriers are within a few dollars of each other, Delta is the one with the record behind it. None of that guarantees an on-time arrival; it moves the odds by 11 points, which is the most any booking decision can do. 1,227 completed flights over 12 months sit behind that.
Common questions
ONT to SLC questions
How often is ONT to SLC delayed?
About one flight in twelve arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 8.9% of the 1,239 flights in this analysis, against 22.7% nationally. Delayed flights are late by an hour and a half on average.
How reliable is ONT to SLC compared with the rest of the country?
91.1% of flights arrive on time here against a national 77.3%, a difference of 14 points in its favour. That is worth a A+ on this site's grading scale.
What time of day has the fewest delays on ONT to SLC?
The 8am–11am departure window is the strongest at 97.4% on time. The 11am–2pm window is the weakest at 86.6%, 11 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 December delays on ONT to SLC?
December is the weakest month at 85.6% on time, compared with 96.5% in May. Across the year that is 11 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 ONT — the return legseparate record
- Ontario International (ONT) delay statistics
- Salt Lake City International (SLC) delay statistics
- SkyWest Airlines on ONT to SLC91.4%
- Delta Air Lines on ONT to SLC91.1%
- ONT to PHX, a related route82.4%
- DEN to SLC, a related route78.2%
- ONT to DEN, a related route81.8%
- SkyWest Airlines on-time record91.4%
- Delta Air Lines on-time record91.1%
- Frontier Airlines on-time record86.7%
- Why the first flight of the morning is statistically safest
- The most punctual routes in the US, and the least
Direction matters. ONT to SLC and SLC to ONT 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.