Carrier route record
WNLAS→ONT
Southwest Airlines · Las Vegas to Ontario
- Flights
- 1,755
- Period
- July 2025 to June 2026
- Share of route
- 71%
- Carriers
- 2
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on LAS to ONT sits in the middle of the pack with a C+. Close to three flights in four arrive on time by the DOT's definition, 4 points worse than the national rate of 77.6%. The late ones land roughly 50 minutes behind schedule. That rests on 1,755 flights, with a median arrival 3 minutes early.
The national on-time rate over the same period is 77.6%, so Southwest on LAS to ONT runs 4 points behind the country as a whole. Across a thousand flights that is about 44 extra late arrivals.
Key figures
On time
73.2%
Arrivals under 15 minutes late, of 1,741 completed flights
Avg delay
49 min
Across delayed arrivals only, not all flights
Cancelled
0.74%
National rate is 1.81%
Whole route
75.8%
Every carrier on LAS to ONT, 2,479 flights
These figures cover 1,755 flights between July 2025 and June 2026. The median arrival is 3 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
Southwest against every carrier on LAS to ONT
Southwest flew 1,755 of the 2,479 flights on LAS to ONT, most of the route. Its 73.2% on time is 3 points worse than the route as a whole, which runs 75.8%. Ranked by on-time rate it is last of two carriers on the route, where the range runs from Frontier at 82.0% to Southwest at 73.2%.
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 |
|---|---|---|---|---|---|
| Frontier Airlines | 724 | 82.0% | 77 min | 0.83% | B+ |
| Southwest Airlines (this page) | 1,755 | 73.2% | 49 min | 0.74% | C+ |
Departure window
When Southwest runs best on this route
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. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am175 flights94.7%
- 8am–11am364 flights85.6%
- 11am–2pm229 flights77.1%
- 2pm–5pm291 flights73.8%
- 5pm–8pm361 flights64.1%
- 8pm–5am335 flights55.3%
Scale runs 45% to 100%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 55.3% on time, against 94.7% 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 8am–11am window is the busiest, with 364 flights scheduled in it.
Across the year
Southwest on LAS to ONT through the year
June is the worst month at 60.7% on time, 22 points below January, the best at 82.6%. 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 157 flights.
Across the week, Tuesday is the strongest day at 82.9% on time and Sunday the weakest at 66.4%. 17 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Southwest runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 62% of the 23,000 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.
- 62%Late-arriving aircraft
- 30%Carrier
- 6%National Airspace System
- 1%Extreme weather
- 1%Security
62% 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 23,000 reported delay minutes here, that single category outweighs weather by 46 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 22,695 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 94.7% on time here.
Cancellations are rare at 0.74%, 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 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 last roughly 50 minutes, 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 is a different operation and performs like one: it runs 77.1% on time across 1,754 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 1,755 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 Southwest on LAS to ONT
Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 82.6% on time and June 60.7%, a swing of 22 points. If the dates move at all, move them out of June before you think about anything else. 1,741 completed flights over 12 months sit behind that.
Related
Where to go next
- LAS to ONT, every carrier
- Southwest on ONT to LAS, the return leg
- Frontier Airlines on LAS to ONT82.0%
- Southwest Airlines network-wide record
- Harry Reid International (LAS) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.