Carrier route record
WNPHX→IAD
Southwest Airlines · Phoenix to Washington
- Flights
- 275
- Period
- September 2025 to August 2026
- Share of route
- 28%
- Carriers
- 2
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on PHX to IAD 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 77.3%. The late ones land about 35 minutes behind schedule. That rests on 275 flights, with a median arrival right on schedule.
The US average over the same twelve months is 77.3%, so there is little to separate Southwest on PHX to IAD from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
74.3%
Arrivals under 15 minutes late, of 272 completed flights
Avg delay
35 min
Across delayed arrivals only, not all flights
Cancelled
0.36%
National rate is 1.89%
Whole route
86.1%
Every carrier on PHX to IAD, 979 flights
These figures cover 275 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 PHX to IAD
Southwest flew 275 of the 979 flights on PHX to IAD, about 28% of it. Its 74.3% on time is 12 points worse than the route as a whole, which runs 86.1%. Ranked by on-time rate it is last of two carriers on the route, where the range runs from United at 90.8% to Southwest at 74.3%.
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 |
|---|---|---|---|---|---|
| United Airlines | 704 | 90.8% | 57 min | 0.71% | A+ |
| Southwest Airlines (this page)thin sample | 275 | 74.3% | 35 min | 0.36% | C+ |
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Departure window
When Southwest runs best on this route
Departure time is the single lever a traveller controls, and it moves the odds more than most people expect. Each bar below is the on-time rate for flights scheduled to leave inside that window, across 275 flights.
- 5am–8am8 flights—
- 8am–11am165 flights73.3%
- 11am–2pm102 flights75.8%
- 2pm–5pm—
- 5pm–8pm—
- 8pm–5am—
Scale runs 65% to 80%. Rows with fewer than 30 flights show a dash.
The 11am–2pm window is the strongest at 75.8% on time. The full set of windows spans 3 points.
Across the year
Southwest on PHX to IAD through the year
- Jul–Sep 202530 flights73.3%
- Oct–Dec 202591 flights73.6%
- Jan–Mar 202690 flights81.6%
- Apr–Jun 202664 flights65.6%
Scale runs 55% to 85%.
Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 74.3% on time across 275 flights.
Southwest on PHX to IAD did not run the same all year. Its best quarter was Jan–Mar 2026 at 81.6% on time and its weakest Apr–Jun 2026 at 65.6%, a swing of 16 points on roughly 69 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.
Across the week, Tuesday is the strongest day at 80.0% on time and Sunday the weakest at 65.8%, a spread of 14 points.
Arrival by arrival
How late Southwest on PHX to IAD runs when it is late
The 70 late arrivals split 34 under half an hour, 30 between 30 and 60 minutes, and 6 an hour or more.
- 15+ min early50 flights18.4%
- Within 15 min152 flights55.9%
- 15–29 min late34 flights12.5%
- 30–59 min late30 flights11.0%
- 1–2 hours late5 flights1.8%
- 2+ hours late1 flights0.4%
Scale runs 0% to 100%.
Share of 272 completed flights by arrival against schedule.
13 of 62 late departures made up the time and arrived on time, 21% of them. In the other direction, 21 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at IAD.
The worst days
Worst days for Southwest on PHX to IAD
The latest arrival of the period was on 1 March 2026, 2 hours 15 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). On three of the five worst days the largest share was filed as a late-arriving aircraft.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 1 March 2026 | 2 hours 15 minutes | Carrier |
| 12 October 2025 | 1 hour 48 minutes | Late-arriving aircraft |
| 2 April 2026 | 1 hour 42 minutes | Late-arriving aircraft |
| 28 April 2026 | 1 hour 7 minutes | Carrier |
| 14 May 2026 | 1 hour 6 minutes | Late-arriving aircraft |
Delay causes
Why Southwest runs late on this route
Carrier accounts for 51% of the 2,425 delay minutes carriers reported here, and the remaining four split what is left.
- 51%Carrier
- 26%Late-arriving aircraft
- 23%National Airspace System
The largest share of delay minutes, 51%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 1,242 of the 2,425 delay minutes reported here. The split is drawn from 2,425 reported delay minutes.
Cancellations are rare at 0.36%, 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
Badly late arrivals are rare here: only 2.2% land an hour or more behind schedule, against 8.3% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.
At 1,956 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.
The return leg is a different operation and performs like one: it runs 71.0% on time across 275 flights, 3 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 3 points of difference.
One caution: this is a thin sample. 275 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 PHX to IAD
Put together: treat all of this as provisional. 275 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 74.3% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 272 completed flights over 12 months sit behind that.
Related
Where to go next
- PHX to IAD, every carrier
- Southwest on IAD to PHX, the return leg
- United Airlines on PHX to IAD90.8%
- Southwest Airlines network-wide record
- Phoenix Sky Harbor International (PHX) delay statistics
- Washington Dulles International (IAD) delay statistics
- The best day of the week to fly, and why it is the second lever
- How to read this site: grades, sample sizes, and honest caveats
Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.