Route reliability record
LAS→ONT
Las Vegas to Ontario
- Flights
- 2,479
- Period
- July 2025 to June 2026
- Distance
- 197 mi
- Carriers
- 2
This route sits in the middle of the pack with a B+. Close to three flights in four arrive on time by the DOT's definition, 2 points worse than the national rate of 77.6%. The late ones land about 55 minutes behind schedule. That rests on 2,479 flights, of which Frontier Airlines flew 724 at 82.0% on time.
The US average over the same twelve months is 77.6%, 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
75.8%
Arrivals under 15 minutes late, of 2,459 completed flights
Avg delay
55 min
Across delayed arrivals only, not all flights
Cancelled
0.77%
National rate is 1.81%
Best carrier
Frontier
82.0% on time across 724 flights
These figures cover 2,479 flights between July 2025 and June 2026. The median arrival is 6 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
Which airline is most reliable on LAS to ONT
The choice of carrier is not cosmetic here. Frontier Airlines arrives on time 82.0% of the time; Southwest Airlines manages 73.2%. Sample sizes sit next to every figure, because a two-point gap across 1,755 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Frontier Airlines | 724 | 82.0% | 77 min | 0.83% | B+ |
| Southwest Airlines | 1,755 | 73.2% | 49 min | 0.74% | C+ |
Frontier leads Southwest by 9 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
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 9 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am273 flights94.1%
- 8am–11am443 flights86.1%
- 11am–2pm348 flights80.3%
- 2pm–5pm426 flights74.1%
- 5pm–8pm530 flights70.0%
- 8pm–5am459 flights59.7%
Scale runs 50% to 100%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 59.7% on time, against 94.1% 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 5pm–8pm window is the busiest, with 530 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 17 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.
June is the worst month at 65.9% on time, 17 points below January, the best at 82.8%. 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. October was the busiest month here, with 228 flights.
Across the week, Tuesday is the strongest day at 83.4% on time and Friday the weakest at 70.8%. 13 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Late-arriving aircraft accounts for 60% of the 33,000 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.
- 60%Late-arriving aircraft
- 31%Carrier
- 7%National Airspace System
- 2%Extreme weather
- 0%Security
60% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 33,000 reported delay minutes here, that single category outweighs weather by 38 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 32,576 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 94.1% on time here.
Cancellations are rare at 0.77%, below the national 1.81% 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
7.1% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route are the about 55 minutes kind, 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 77.5% on time across 2,479 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 2,479 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.
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 82.8% on time and June 65.9%, a swing of 17 points. If the dates move at all, move them out of June before you think about anything else. 2,459 completed flights over 12 months sit behind that.
Common questions
LAS to ONT questions
How often is LAS to ONT delayed?
About one flight in four arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 24.2% of the 2,479 flights in this analysis, against 22.4% nationally. Delayed flights are late by about 55 minutes on average.
Which airline is most reliable on LAS to ONT?
Frontier Airlines leads at 82.0% on time across 724 flights. Southwest Airlines is at the other end on 73.2%, a gap of 9 points. 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 LAS to ONT?
The 5am–8am departure window is the strongest at 94.1% on time. The 8pm–5am window is the weakest at 59.7%, 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 June delays on LAS to ONT?
June is the weakest month at 65.9% on time, compared with 82.8% in January. Across the year that is 17 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 LAS — the return legseparate record
- Harry Reid International (LAS) delay statistics
- Frontier Airlines on-time record82.0%
- Southwest Airlines on-time record73.2%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Direction matters. LAS to ONT and ONT to LAS are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.