Carrier route record

WNONT→LAS

Southwest Airlines · Ontario to Las Vegas

Flights: 1,754
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 ONT to LAS lands a B+, level with the national rate of 77.6%. Roughly one flight in four arrives 15 minutes late or worse, and those flights are late by roughly 55 minutes on average. That is a workable record, not a spotless one. That rests on 1,754 flights, with a median arrival 4 minutes early.

The US average over the same twelve months is 77.6%, so there is little to separate Southwest on ONT to LAS from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

77.1%

Arrivals under 15 minutes late, of 1,742 completed flights

Avg delay

53 min

Across delayed arrivals only, not all flights

Cancelled

0.68%

National rate is 1.81%

Whole route

77.5%

Every carrier on ONT to LAS, 2,479 flights

These figures cover 1,754 flights between July 2025 and June 2026. The median arrival is 4 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 ONT to LAS

Southwest flew 1,754 of the 2,479 flights on ONT to LAS, most of the route. Its 77.1% on time is about level with the route as a whole at 77.5%. Ranked by on-time rate it is last of two carriers on the route, where the range runs from Frontier at 78.4% to Southwest at 77.1%.

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.

On-time performance by carrier on ONT to LAS
Airline	Flights	On time	Avg delay	Cancelled	Grade
Frontier Airlines	725	78.4%	93 min	1.24%	B
Southwest Airlines (this page)	1,754	77.1%	53 min	0.68%	B+

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 34 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–8am353 flights96.9%
8am–11am334 flights88.2%
11am–2pm229 flights73.4%
2pm–5pm362 flights62.6%
5pm–8pm159 flights66.0%
8pm–5am317 flights68.3%

Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 96.9% of the time, against 62.6% for the afternoon window. That is 34 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 2pm–5pm window is the busiest, with 362 flights scheduled in it.

Across the year

Southwest on ONT to LAS through the year

Darker means more delays. Figures are on-time percentages.February best, May worst

Delays peak in May, when the on-time rate falls to 60.1%. February is the strongest month at 89.0%. Moving a flexible trip across that boundary buys 29 points. July was the busiest month here, with 157 flights.

Across the week, Saturday is the strongest day at 86.0% on time and Friday the weakest at 65.7%. 20 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 53% of the 21,000 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.

Late-arriving aircraft
53%
National Airspace System
33%
Carrier
13%
Extreme weather
0%
Security
0%

53% 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 21,000 reported delay minutes here, that single category outweighs weather by 53 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 21,103 reported delay minutes.

33% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 6,892 minutes out of 21,000, against a national NAS share of 21%.

Cancellations are rare at 0.68%, 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

6.4% 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 55 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 73.2% on time across 1,755 flights, 4 points below 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 1,754 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 ONT to LAS

Put together: the calendar is the biggest lever here, not the carrier or the hour. February runs 89.0% on time and May 60.1%, a swing of 29 points. If the dates move at all, move them out of May before you think about anything else. 1,742 completed flights over 12 months sit behind that.

Where to go next

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.

Key figures