Carrier route record
WNSFO→PHX
Southwest Airlines · San Francisco to Phoenix
- Flights
- 1,079
- Period
- July 2025 to June 2026
- Share of route
- 23%
- Carriers
- 5
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on SFO to PHX draws a D+. Roughly one flight in three arrives at least 15 minutes late, and the typical late arrival is about an hour behind schedule. Build slack into anything you connect to. That rests on 1,079 flights. The strongest carrier on the route with a full sample, SkyWest Airlines, flew 538 at 87.3% on time.
SkyWest Airlines is the most reliable of the three carriers covered here at 87.3% on time across 538 flights.
Key figures
On time
61.1%
Arrivals under 15 minutes late, of 1,073 completed flights
Avg delay
57 min
Across delayed arrivals only, not all flights
Cancelled
0.56%
National rate is 1.81%
Whole route
74.4%
Every carrier on SFO to PHX, 4,643 flights
These figures cover 1,079 flights between July 2025 and June 2026. Beyond the headline rate, 12.2% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
Carrier by carrier
Southwest against every carrier on SFO to PHX
Southwest flew 1,079 of the 4,643 flights on SFO to PHX, about 23% of it. Its 61.1% on time is 13 points worse than the route as a whole, which runs 74.4%. Ranked by on-time rate it is number four of five carriers on the route, where the range runs from SkyWest at 87.3% to Frontier at 59.6%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The choice of carrier is not cosmetic here. SkyWest Airlines arrives on time 87.3% of the time; American Airlines manages 75.7%. Sample sizes sit next to every figure, because a two-point gap across 1,320 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| SkyWest Airlines | 538 | 87.3% | 67 min | 0.74% | A+ |
| United Airlines | 1,443 | 81.0% | 59 min | 0.49% | B+ |
| American Airlines | 1,320 | 75.7% | 106 min | 0.83% | B+ |
| Southwest Airlines (this page) | 1,079 | 61.1% | 57 min | 0.56% | D+ |
| Frontier Airlinesthin sample | 263 | 59.6% | 98 min | 3.04% | D− |
SkyWest leads American by 12 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
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 66 points, against 12 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am324 flights93.8%
- 8am–11am131 flights60.3%
- 11am–2pm255 flights48.8%
- 2pm–5pm251 flights47.2%
- 5pm–8pm89 flights28.1%
- 8pm–5am29 flights—
Scale runs 20% to 100%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 28.1% on time, against 93.8% 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 5am–8am window is the busiest, with 324 flights scheduled in it.
Across the year
Southwest on SFO to PHX through the year
Delays peak in May, when the on-time rate falls to 38.0%. January is the strongest month at 84.2%. Moving a flexible trip across that boundary buys 46 points. January was the busiest month here, with 95 flights.
Across the week, Tuesday is the strongest day at 72.7% on time and Thursday the weakest at 53.9%. 19 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 61% of the 24,000 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.
- 61%Late-arriving aircraft
- 31%Carrier
- 8%National Airspace System
- 0%Extreme weather
61% 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 24,000 reported delay minutes here, that single category outweighs weather by 61 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 23,618 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 93.8% on time here.
Cancellations are rare at 0.56%, 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
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 12.2% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.
The 651 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.
The return leg runs 60.5% on time across 1,079 flights, within half a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
One caution: this is a thin sample. 1,079 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.
What to do with this
Booking Southwest on SFO to PHX
Put together: treat all of this as provisional. 1,079 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 61.1% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 1,073 completed flights over 12 months sit behind that.
Related
Where to go next
- SFO to PHX, every carrier
- Southwest on PHX to SFO, the return leg
- SkyWest Airlines on SFO to PHX87.3%
- United Airlines on SFO to PHX81.0%
- American Airlines on SFO to PHX75.7%
- Frontier Airlines on SFO to PHX59.6%
- Southwest Airlines network-wide record
- San Francisco International (SFO) delay statistics
- Phoenix Sky Harbor International (PHX) delay statistics
- Why the first flight of the morning is statistically safest
- Same route, different airline: where the carrier you pick matters most
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.