Route reliability record
ONT→LAS
Ontario to Las Vegas
- Flights
- 2,479
- Period
- July 2025 to June 2026
- Distance
- 197 mi
- Carriers
- 2
This route lands a B+, level with the national rate of 77.6%. Roughly one flight in four arrive 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 2,479 flights, of which Frontier Airlines flew 725 at 78.4% 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
77.5%
Arrivals under 15 minutes late, of 2,458 completed flights
Avg delay
64 min
Across delayed arrivals only, not all flights
Cancelled
0.85%
National rate is 1.81%
Best carrier
Frontier
78.4% on time across 725 flights
These figures cover 2,479 flights between July 2025 and June 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.
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 |
|---|---|---|---|---|---|
| Frontier Airlines | 725 | 78.4% | 93 min | 1.24% | B |
| Southwest Airlines | 1,754 | 77.1% | 53 min | 0.68% | B+ |
No carrier stands out. Frontier tops the table at 78.4%, about a point clear of the bottom, which is inside the range this kind of sample moves year to year.
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 31 points, against about a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am500 flights95.0%
- 8am–11am402 flights88.7%
- 11am–2pm339 flights74.3%
- 2pm–5pm501 flights68.4%
- 5pm–8pm319 flights64.0%
- 8pm–5am418 flights69.5%
Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 64.0% on time, against 95.0% 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 501 flights scheduled in it.
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 86.3% on time and Friday the weakest at 65.8%. 21 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 55% of the 36,000 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.
- 55%Late-arriving aircraft
- 28%National Airspace System
- 16%Carrier
- 1%Extreme weather
- 0%Security
55% 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 36,000 reported delay minutes here, that single category outweighs weather by 55 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 35,579 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 95.0% on time here.
Cancellations are rare at 0.85%, 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
7.6% 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 an hour 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 75.8% 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. 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. 2,458 completed flights over 12 months sit behind that.
Common questions
ONT to LAS questions
How often is ONT to LAS delayed?
Roughly 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 22.5% of the 2,479 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on ONT to LAS?
Frontier Airlines leads at 78.4% on time across 725 flights. Southwest Airlines is at the other end on 77.1%, 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 95.0% on time. The 5pm–8pm window is the weakest at 64.0%, 31 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
- Harry Reid International (LAS) delay statistics
- Frontier Airlines on-time record78.4%
- Southwest Airlines on-time record77.1%
- 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. 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.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.