Route reliability record
SJC→ONT
San Jose to Ontario
- Flights
- 1,318
- Period
- September 2025 to August 2026
- Distance
- 333 mi
- Carriers
- 1
This route lands a B+, 5 points better than the national rate of 77.3%. About one flight in six arrives 15 minutes late or worse, and those flights are late by about 45 minutes on average. That rests on 1,318 SJC to ONT flights, with a median arrival 8 minutes early.
Best time to fly SJC to ONT: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 97.9% of the time and Tuesday flights 88.5%, against 82.4% for the route overall.
Set against the rest of the country, this route's record is 5 points better than the US average of 77.3%. That gap is worth roughly 51 fewer late arrivals for every thousand flights.
Key figures
On time
82.4%
Arrivals under 15 minutes late, of 1,315 completed flights
Avg delay
46 min
Across delayed arrivals only, not all flights
Cancelled
0.15%
National rate is 1.89%
Best carrier
Southwest
82.4% on time across 1,318 flights
These figures cover 1,318 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
Which airline is most reliable on SJC to ONT
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 |
|---|---|---|---|---|---|
| Southwest Airlines | 1,318 | 82.4% | 46 min | 0.15% | B+ |
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Best ways to make this trip
The most reliable ways to fly San Jose to Ontario
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. 5 of the top 5 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. SJC → LAXSan Jose to Los Angeles | SkyWest Airlines | 91.3% | 91.7% | 0.44% | 5am–8am, Tue | OO 3883 20:05 |
| 2. SJC → LAXSan Jose to Los Angeles | Delta Air Lines | 89.5% | 91.6% | 2.31% | 11am–2pm, Tue | — |
| 3. MRY → LAXMonterey to Los Angeles | SkyWest Airlines | 86.2% | 86.8% | 0.70% | 5pm–8pm, Wed | — |
| 4. SJC → SNASan Jose to Santa Ana | Southwest Airlines | 85.9% | 86.6% | 0.78% | 5am–8am, Sat (route) | — |
| 5. OAK → LGBOakland to Long Beach | Southwest Airlines | 85.4% | 85.7% | 0.32% | 5am–8am, 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 39 points, against half a point between the best and worst carrier.
- 5am–8am288 flights97.9%
- 8am–11am206 flights92.2%
- 11am–2pm230 flights87.4%
- 2pm–5pm177 flights76.3%
- 5pm–8pm216 flights74.1%
- 8pm–5am201 flights58.5%
Scale runs 50% to 100%.
The 8pm–5am window is where this operation falls apart: 58.5% on time, against 97.9% for the 5am–8am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 5am–8am window is the busiest, with 288 flights scheduled in it.
Explore
Filter SJC to ONT 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 SJC to ONT, the best departure window is 5am–8am at 97.9% on time and the worst is 8pm–5am at 58.5%, a wide gap of 39.4 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am97.9%
- 8–11am92.2%
- 11am–2pm87.4%
- 2–5pm76.3%
- 5–8pm74.1%
- 8pm–5am58.5%
best all US flightsScale 50% to 100%.
Across the year
When delays peak on this route
This route's year swings by 20 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.
July is the worst month at 70.3% on time, 20 points below January, the best at 90.1%. 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. July was the busiest month here, with 119 flights.
Across the week, Tuesday is the strongest day at 88.5% on time and Sunday the weakest at 74.6%, a spread of 14 points.
Delay causes
Why this route gets delayed
Late-arriving aircraft accounts for 75% of the 11,000 delay minutes carriers reported here, and the remaining four split what is left.
- 75%Late-arriving aircraft
- 22%Carrier
- 3%National Airspace System
- 0%Extreme weather
75% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 11,000 reported delay minutes here, that single category outweighs weather by 75 to one. The split is drawn from 10,674 reported delay minutes.
The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 97.9% on time here.
Cancellations are rare at 0.15%, 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 3.5% 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.
At 333 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 is a different operation and performs like one: it runs 85.9% on time across 1,320 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.
The sample behind these figures is 1,318 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 ONT 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. January runs 90.1% on time and July 70.3%, a swing of 20 points. If the dates move at all, move them out of July before you think about anything else. 1,315 completed flights over 12 months sit behind that.
Common questions
SJC to ONT questions
How often is SJC to ONT delayed?
About one flight in six arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 17.6% of the 1,318 flights in this analysis, against 22.7% nationally. Delayed flights are late by about 45 minutes on average.
How reliable is SJC to ONT compared with the rest of the country?
82.4% of flights arrive on time here against a national 77.3%, a difference of 5 points in its favour. That is worth a B+ on this site's grading scale.
What time of day has the fewest delays on SJC to ONT?
The 5am–8am departure window is the strongest at 97.9% on time. The 8pm–5am window is the weakest at 58.5%, 39 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 July delays on SJC to ONT?
July is the weakest month at 70.3% on time, compared with 90.1% in January. Across the year that is 20 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
- ONT to SJC — the return legseparate record
- Norman Y. Mineta San Jose International (SJC) delay statistics
- Ontario International (ONT) delay statistics
- SJC to SAN, a related route68.3%
- PHX to ONT, a related route76.8%
- SJC to LAX, a related route85.0%
- Southwest Airlines on-time record82.4%
- 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. SJC to ONT and ONT to SJC 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.