Route reliability record
IAD→PHX
Washington to Phoenix
- Flights
- 1,097
- Period
- July 2025 to June 2026
- Distance
- 1,956 mi
- Carriers
- 2
This route lands a B+, 2 points better than the national rate of 77.6%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 1,097 IAD to PHX flights, with a median arrival 7 minutes early.
Best time to fly IAD to PHX: a 8am–11am departure, ideally on a Tuesday. Flights in that window arrived on time 95.9% of the time and Tuesday flights 84.1%, against 79.9% for the route overall.
The US average over the same twelve months is 77.6%, 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
79.9%
Arrivals under 15 minutes late, of 1,086 completed flights
Avg delay
63 min
Across delayed arrivals only, not all flights
Cancelled
0.82%
National rate is 1.81%
Best carrier
United
84.9% on time across 760 flights
These figures cover 1,097 flights between July 2025 and June 2026. The median arrival is 7 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
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 | 760 | 84.9% | 77 min | 0.79% | B+ |
| Southwest Airlinesthin sample | 337 | 68.7% | 48 min | 0.89% | 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.
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 | 84.2% | 84.9% | 0.79% | 8am–11am, Tue | UA 1938 17:26 |
| 2. DCA → PHXWashington to Phoenix | American Airlines | 81.1% | 82.3% | 1.47% | 5am–8am, Tue | AA 1218 10:05 |
| 3. BWI → PHXBaltimore to Phoenix | Southwest Airlines | 75.2% | 76.0% | 1.09% | 5am–8am, Tue | — |
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 25 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–8am9 flights—
- 8am–11am199 flights95.9%
- 11am–2pm202 flights87.0%
- 2pm–5pm180 flights78.5%
- 5pm–8pm507 flights71.2%
- 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 95.9% of the time, against 71.2% for the evening window. That is 25 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 507 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 31 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.
July is the worst month at 58.9% on time, 31 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 84.1% on time and Wednesday the weakest at 73.7%. 10 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Late-arriving aircraft accounts for 43% of the 14,000 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.
- 43%Late-arriving aircraft
- 28%National Airspace System
- 24%Carrier
- 5%Extreme weather
43% 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 14,000 reported delay minutes here, that single category outweighs weather by 8 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 13,800 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 95.9% on time here.
Cancellations are rare at 0.82%, 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 actually costs
5.6% 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 about an hour, which a normal layover absorbs.
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 84.7% on time across 1,098 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.
The sample behind these figures is 1,097 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.
Work out the risk of missing a connection in PHX after this flight
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 89.4% on time and July 58.9%, a swing of 31 points. If the dates move at all, move them out of July before you think about anything else. 1,086 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 20.1% of the 1,097 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
How reliable is IAD to PHX compared with the rest of the country?
79.9% of flights arrive on time here against a national 77.6%, a difference of 2 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 95.9% on time. The 5pm–8pm window is the weakest at 71.2%, 25 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 July delays on IAD to PHX?
July is the weakest month at 58.9% on time, compared with 89.4% in January. Across the year that is 31 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 PHX84.9%
- Southwest Airlines on IAD to PHX68.7%
- IAD to ATL, a related route79.2%
- DEN to PHX, a related route75.7%
- IAD to DEN, a related route81.7%
- United Airlines on-time record84.9%
- Southwest Airlines on-time record68.7%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.