Carrier route record

WNSEA→PHX

Southwest Airlines · Seattle to Phoenix

Flights: 1,042
Period: September 2025 to August 2026
Share of route: 14%
Carriers: 7

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

Southwest on SEA to PHX draws a C+. About one flight in three arrives at least 15 minutes late, and the typical late arrival is roughly 50 minutes behind schedule. Build slack into anything you connect to. That rests on 1,042 flights. The strongest carrier on the route with a full sample, Envoy Air, flew 760 at 85.3% on time.

Envoy Air is the most reliable of the four carriers covered here at 85.3% on time across 760 flights.

On time

65.1%

Arrivals under 15 minutes late, of 1,031 completed flights

Avg delay

49 min

Across delayed arrivals only, not all flights

Cancelled

0.77%

National rate is 1.89%

Whole route

78.2%

Every carrier on SEA to PHX, 7,205 flights

These figures cover 1,042 flights between September 2025 and August 2026. On-time means an arrival less than 15 minutes after the scheduled gate time, the same threshold the Department of Transportation uses in its own reports. Cancelled and diverted flights are excluded from the on-time rate and counted separately, which is why the cancellation column matters on its own.

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Carrier by carrier

Southwest against every carrier on SEA to PHX

Southwest flew 1,042 of the 7,205 flights on SEA to PHX, about 14% of it. Its 65.1% on time is 13 points worse than the route as a whole, which runs 78.2%. Ranked by on-time rate it is last of seven carriers on the route, where the range runs from Envoy at 85.3% to Southwest at 65.1%. Two of those carriers flew fewer than 365 flights here, so treat their positions as rough.

The choice of carrier is not cosmetic here. Envoy Air arrives on time 85.3% of the time; SkyWest Airlines manages 78.5%. Sample sizes sit next to every figure, because a two-point gap across 409 flights means less than a ten-point one.

On-time performance by carrier on SEA to PHX
Airline	Flights	On time	Avg delay	Cancelled	Grade
Envoy Air	760	85.3%	74 min	0.00%	A+
American Airlinesthin sample	221	83.2%	76 min	0.45%	B+
Delta Air Lines	1,768	80.9%	67 min	0.96%	B+
Alaska Airlines	2,889	79.2%	45 min	0.66%	B+
SkyWest Airlines	409	78.5%	80 min	0.49%	B+
Frontier Airlinesthin sample	116	74.5%	146 min	5.17%	C−
Southwest Airlines (this page)	1,042	65.1%	49 min	0.77%	C+

Envoy leads SkyWest by 7 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.

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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 67 points, against 7 points between the best and worst carrier.

5am–8am350 flights93.4%
8am–11am97 flights69.8%
11am–2pm254 flights53.2%
2pm–5pm136 flights47.4%
5pm–8pm156 flights45.4%
8pm–5am49 flights26.5%

Scale runs 20% to 100%.

The 8pm–5am window is where this operation falls apart: 26.5% on time, against 93.4% 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 350 flights scheduled in it.

Across the year

Southwest on SEA to PHX through the year

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

August is the worst month at 41.5% on time, 45 points below January, the best at 86.4%. 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 107 flights.

Across the week, Tuesday is the strongest day at 73.4% on time and Thursday the weakest at 57.5%, a spread of 16 points.

Arrival by arrival

How late Southwest on SEA to PHX runs when it is late

The 360 late arrivals split 153 under half an hour, 127 between 30 and 60 minutes, and 80 an hour or more.

15+ min early83 flights8.1%
Within 15 min588 flights57.0%
15–29 min late153 flights14.8%
30–59 min late127 flights12.3%
1–2 hours late56 flights5.4%
2+ hours late24 flights2.3%

Scale runs 0% to 100%.

Share of 1,031 completed flights by arrival against schedule.

89 of 401 late departures made up the time and arrived on time, 22% of them. 48 flights left on time and still arrived late.

The worst days

Worst days for Southwest on SEA to PHX

The latest arrival of the period was on 6 March 2026, 6 hours 45 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. The same cause led on three of the five worst days.

The latest arrivals of Southwest on SEA to PHX in the period
Date	Arrived late by	Largest filed cause
6 March 2026	6 hours 45 minutes	Late-arriving aircraft
19 June 2026	4 hours 20 minutes	Late-arriving aircraft
16 July 2026	3 hours 56 minutes	Carrier
19 September 2025	3 hours 46 minutes	Carrier
29 April 2026	3 hours 31 minutes	Late-arriving aircraft

Delay causes

Why Southwest runs late on this route

Late-arriving aircraft accounts for 54% of the 18,000 delay minutes carriers reported here, and the remaining four split what is left.

Late-arriving aircraft
54%
Carrier
31%
National Airspace System
14%
Security
1%
Extreme weather
0%

54% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 18,000 reported delay minutes here, that single category outweighs weather by 54 to one. The split is drawn from 17,608 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 93.4% on time here.

Cancellations are rare at 0.77%, below the national 1.89% 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

7.8% of arrivals land an hour or more late, close to the national 8.3%, so 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.

The 1,107 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.

The return leg runs 62.2% on time across 1,039 flights, within 3 points 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. 1,042 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 SEA to PHX

Put together: treat all of this as provisional. 1,042 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 65.1% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 1,031 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated 22 October 2026; recomputed monthly. How this data is collected.

Key figures