Route reliability record
ONT→LAS
Ontario to Las Vegas
- Flights
- 2,469
- Period
- September 2025 to August 2026
- Distance
- 197 mi
- Carriers
- 2
This route lands a B+, about a point worse than the national rate of 77.3%. About one flight in four arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 2,469 ONT to LAS flights, of which Southwest Airlines flew 1,744 at 76.6% on time.
Best time to fly ONT to LAS: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 95.8% of the time and Saturday flights 84.0%, against 76.2% for the route overall.
The US average over the same twelve months is 77.3%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
76.2%
Arrivals under 15 minutes late, of 2,445 completed flights
Avg delay
60 min
Across delayed arrivals only, not all flights
Cancelled
0.93%
National rate is 1.89%
Best carrier
Southwest
76.6% on time across 1,744 flights
These figures cover 2,469 flights between September 2025 and August 2026. The median arrival is 5 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 LAS
The two carriers here are closely matched: about a point separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Southwest Airlines | 1,744 | 76.6% | 51 min | 0.80% | B+ |
| Frontier Airlines | 725 | 75.4% | 83 min | 1.24% | B |
No carrier stands out. Southwest tops the table at 76.6%, about a point clear of the bottom, which is inside the range this kind of sample moves year to year.
Flight by flight
Flights on ONT to LAS
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.
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Best ways to make this trip
The most reliable ways to fly Ontario to Las Vegas
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. SNA → LASSanta Ana to Las Vegas | Spirit Airlines | 88.1% | 89.9% | 1.98% | 5am–8am, Sat | — |
| 2. SNA → LASSanta Ana to Las Vegas | SkyWest Airlines | 85.9% | 86.5% | 0.69% | 11am–2pm, Wed | OO 4078 09:59 |
| 3. LAX → LASLos Angeles to Las Vegas | United Airlines | 82.7% | 83.1% | 0.51% | 8am–11am, Wed | UA 1006 08:15 |
| 4. LAX → LASLos Angeles to Las Vegas | Spirit Airlines | 81.8% | 82.9% | 1.31% | 5am–8am, Wed | — |
| 5. BUR → LASBurbank to Las Vegas | Spirit Airlines | 81.4% | 84.0% | 3.13% | 2pm–5pm, 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 34 points, against about a point between the best and worst carrier.
- 5am–8am452 flights95.8%
- 8am–11am386 flights89.5%
- 11am–2pm405 flights70.7%
- 2pm–5pm567 flights67.0%
- 5pm–8pm264 flights62.2%
- 8pm–5am395 flights69.3%
Scale runs 55% to 100%.
The 5pm–8pm window is where this operation falls apart: 62.2% on time, against 95.8% 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 2pm–5pm window is the busiest, with 567 flights scheduled in it.
Explore
Filter ONT to LAS 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 LAS, the best departure window is 5am–8am at 95.8% on time and the worst is 5pm–8pm at 62.2%, a wide gap of 33.6 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am95.8%
- 8–11am89.5%
- 11am–2pm70.7%
- 2–5pm67.0%
- 5–8pm62.2%
- 8pm–5am69.3%
best all US flightsScale 55% to 100%.
Across the year
When delays peak on this route
This route's year swings by 24 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.
Delays peak in May, when the on-time rate falls to 64.3%. February is the strongest month at 88.5%. Moving a flexible trip across that boundary buys 24 points. October was the busiest month here, with 228 flights.
Across the week, Saturday is the strongest day at 84.0% on time and Friday the weakest at 67.8%, a spread of 16 points.
Delay causes
Why this route gets delayed
Late-arriving aircraft accounts for 56% of the 35,000 delay minutes carriers reported here, and the remaining four split what is left.
- 56%Late-arriving aircraft
- 28%National Airspace System
- 15%Carrier
- 1%Extreme weather
- 0%Security
56% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 35,000 reported delay minutes here, that single category outweighs weather by 56 to one. The split is drawn from 35,118 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 95.8% on time here.
Cancellations sit at 0.93% against a national 1.89%, which is ordinary. Diversions add another 0.04%.
Connections and stage length
What a delay here actually costs
7.4% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, which a normal layover absorbs.
At 197 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 runs 75.4% on time across 2,473 flights, within about a point 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 2,469 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 LAS 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. February runs 88.5% on time and May 64.3%, a swing of 24 points. If the dates move at all, move them out of May before you think about anything else. 2,445 completed flights over 12 months sit behind that.
Common questions
ONT to LAS questions
How often is ONT to LAS delayed?
About one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 23.8% of the 2,469 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on ONT to LAS?
Southwest Airlines leads at 76.6% on time across 1,744 flights. Frontier Airlines is at the other end on 75.4%, a gap of about a point. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on ONT to LAS?
The 5am–8am departure window is the strongest at 95.8% on time. The 5pm–8pm window is the weakest at 62.2%, 34 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 May delays on ONT to LAS?
May is the weakest month at 64.3% on time, compared with 88.5% in February. Across the year that is 24 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
- LAS to ONT — the return legseparate record
- Ontario International (ONT) delay statistics
- Harry Reid International (LAS) delay statistics
- Southwest Airlines on ONT to LAS76.6%
- Frontier Airlines on ONT to LAS75.4%
- ONT to PHX, a related route82.4%
- LAX to LAS, a related route75.8%
- ONT to DEN, a related route81.8%
- Southwest Airlines on-time record76.6%
- Frontier Airlines on-time record75.4%
- 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. ONT to LAS and LAS 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.