Route reliability record
IAD→PHX
Washington to Phoenix
- Flights
- 979
- Period
- September 2025 to August 2026
- Distance
- 1,956 mi
- Carriers
- 2
This route lands a B+, 4 points better than the national rate of 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 979 IAD to PHX flights, with a median arrival 8 minutes early.
Best time to fly IAD to PHX: a 8am–11am departure, ideally on a Tuesday. Flights in that window arrived on time 96.6% of the time and Tuesday flights 86.6%, against 81.2% for the route overall.
The US average over the same twelve months is 77.3%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
81.2%
Arrivals under 15 minutes late, of 969 completed flights
Avg delay
57 min
Across delayed arrivals only, not all flights
Cancelled
0.82%
National rate is 1.89%
Best carrier
United
85.2% on time across 704 flights
These figures cover 979 flights between September 2025 and August 2026. The median arrival is 8 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.
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Carrier by carrier
Which airline is most reliable on IAD to PHX
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 | 85.2% | 66 min | 0.85% | A+ |
| Southwest Airlinesthin sample | 275 | 71.0% | 45 min | 0.73% | C+ |
Flight by flight
Flights on IAD to PHX
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
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Best ways to make this trip
The most reliable ways to fly Washington to Phoenix
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 2 of the top 3 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. IAD → PHXWashington to Phoenix | United Airlines | 84.5% | 85.2% | 0.85% | 8am–11am, Tue | UA 1938 17:50 |
| 2. DCA → PHXWashington to Phoenix | American Airlines | 81.3% | 82.5% | 1.47% | 5am–8am, Tue | AA 1218 10:00 |
| 3. BWI → PHXBaltimore to Phoenix | Southwest Airlines | 75.6% | 76.4% | 1.07% | 5am–8am, Thu | — |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 22 points, against half a point between the best and worst carrier.
- 5am–8am9 flights—
- 8am–11am150 flights96.6%
- 11am–2pm194 flights87.0%
- 2pm–5pm156 flights79.2%
- 5pm–8pm470 flights74.4%
- 8pm–5am—
Scale runs 65% to 100%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 96.6% of the time, against 74.4% for the evening window. That is 22 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5pm–8pm window is the busiest, with 470 flights scheduled in it.
Explore
Filter IAD to PHX by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On IAD to PHX, the best departure window is 8am–11am at 96.6% on time and the worst is 5pm–8pm at 74.4%, a wide gap of 22.2 points. All US flights leaving 8am–11am ran 83.9%.
- 5–8am—
- 8–11am96.6%
- 11am–2pm87.0%
- 2–5pm79.2%
- 5–8pm74.4%
- 8pm–5am—
best all US flightsScale 60% to 100%. Cells under 30 flights show a dash.
Across the year
When delays peak on this route
This route's year swings by 18 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
August is the worst month at 71.0% on time, 18 points below January, the best at 89.4%. 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. March was the busiest month here, with 117 flights.
Across the week, Tuesday is the strongest day at 86.6% on time and Friday the weakest at 77.6%, a spread of 9 points.
Delay causes
Why this route gets delayed
Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 10,000 reported delay minutes.
- 38%National Airspace System
- 37%Late-arriving aircraft
- 23%Carrier
- 2%Extreme weather
37% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 10,000 reported delay minutes here, that single category outweighs weather by 19 to one. The split is drawn from 10,383 reported delay minutes.
38% 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 3,936 minutes out of 10,000, against a national NAS share of 21%.
Cancellations are rare at 0.82%, 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 actually costs
Badly late arrivals are rare here: only 4.7% 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 86.1% on time across 979 flights, 5 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 5 points of difference.
One caution: this is a thin sample. 979 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.
Work out the risk of missing a connection in PHX after this flight
What to do with this
Booking this route
Put together: treat all of this as provisional. 979 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 81.2% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 969 completed flights over 12 months sit behind that.
Common questions
IAD to PHX questions
How often is IAD to PHX delayed?
About one flight in five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 18.8% of the 979 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
How reliable is IAD to PHX compared with the rest of the country?
81.2% of flights arrive on time here against a national 77.3%, a difference of 4 points in its favour. That is worth a B+ on this site's grading scale.
What time of day has the fewest delays on IAD to PHX?
The 8am–11am departure window is the strongest at 96.6% on time. The 5pm–8pm window is the weakest at 74.4%, 22 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are August delays on IAD to PHX?
August is the weakest month at 71.0% on time, compared with 89.4% in January. Across the year that is 18 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- PHX to IAD — the return legseparate record
- Washington Dulles International (IAD) delay statistics
- Phoenix Sky Harbor International (PHX) delay statistics
- United Airlines on IAD to PHX85.2%
- Southwest Airlines on IAD to PHX71.0%
- IAD to ATL, a related route78.0%
- DEN to PHX, a related route75.6%
- IAD to DEN, a related route83.1%
- United Airlines on-time record85.2%
- Southwest Airlines on-time record71.0%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
Direction matters. IAD to PHX and PHX to IAD are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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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.