Carrier route record

WNPHX→ONT

Southwest Airlines · Phoenix to Ontario

Flights: 1,608
Period: July 2025 to June 2026
Share of route: 53%
Carriers: 4

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.

Southwest on PHX 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, 3 points worse than the national rate of 77.6%. The late ones land roughly 50 minutes behind schedule. That rests on 1,608 flights, with a median arrival 2 minutes early.

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

On time

74.4%

Arrivals under 15 minutes late, of 1,605 completed flights

Avg delay

49 min

Across delayed arrivals only, not all flights

Cancelled

0.19%

National rate is 1.81%

Whole route

77.7%

Every carrier on PHX to ONT, 3,059 flights

These figures cover 1,608 flights between July 2025 and June 2026. The median arrival is 2 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 PHX to ONT

Southwest flew 1,608 of the 3,059 flights on PHX to ONT, most of the route. Its 74.4% on time is 3 points worse than the route as a whole, which runs 77.7%. Ranked by on-time rate it is last of four carriers on the route, where the range runs from SkyWest at 91.1% to Southwest at 74.4%. Two of those carriers flew fewer than 365 flights here, so treat their positions as rough.

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 PHX to ONT
Airline	Flights	On time	Avg delay	Cancelled	Grade
SkyWest Airlinesthin sample	91	91.1%	60 min	1.10%	A
Envoy Airthin sample	45	91.1%	37 min	0.00%	A+
American Airlines	1,315	80.4%	67 min	0.91%	B+
Southwest Airlines (this page)	1,608	74.4%	49 min	0.19%	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 40 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–8am60 flights96.7%
8am–11am404 flights90.8%
11am–2pm220 flights81.4%
2pm–5pm309 flights75.3%
5pm–8pm187 flights61.8%
8pm–5am428 flights56.9%

Scale runs 50% to 100%. Rows with fewer than 30 flights show a dash.

The 8pm–5am window is where this operation falls apart: 56.9% on time, against 96.7% 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 8pm–5am window is the busiest, with 428 flights scheduled in it.

Across the year

Southwest on PHX to ONT through the year

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

Delays peak in May, when the on-time rate falls to 61.2%. January is the strongest month at 86.8%. Moving a flexible trip across that boundary buys 26 points. December was the busiest month here, with 145 flights.

Across the week, Tuesday is the strongest day at 81.9% on time and Friday the weakest at 69.6%. 12 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 60% of the 20,000 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
60%
Carrier
36%
National Airspace System
4%
Security
0%
Extreme weather
0%

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 20,000 reported delay minutes here, that single category outweighs weather by 60 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 20,067 reported delay minutes.

The largest share of delay minutes, 36%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 7,182 of the 20,000 delay minutes reported here.

Cancellations are rare at 0.19%, 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

6.3% 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 325 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 81.5% on time across 1,608 flights, 7 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 7 points of difference.

The sample behind these figures is 1,608 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 PHX to ONT

Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 86.8% on time and May 61.2%, a swing of 26 points. If the dates move at all, move them out of May before you think about anything else. 1,605 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