Washington, DC · departure reliability
IAD
Washington Dulles International
- Departures
- 58,239
- Period
- June 2025 to May 2026
- Carriers
- 10
- US rank
- #33 by volume
Washington
Washington Dulles International lands a B, 3 points better than the national rate of 77.4%. About one flight in five arrive 15 minutes late or worse, and those flights are late by a little over an hour on average. That is a workable record, not a spotless one. That rests on 58,239 flights, of which PSA Airlines flew 1,121 at 83.1% on time.
PSA Airlines is the most reliable of the ten carriers covered here at 83.1% on time across 1,121 flights.
Key figures
On time
80.3%
Departures arriving under 15 minutes late at their destination
Avg delay
80 min
Across delayed flights only
Cancelled
1.39%
National rate is 1.80%
Best carrier
PSA
83.1% on time here
These figures cover 58,000 flights between June 2025 and May 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.
Carrier by carrier
Which airlines run best out of IAD
The choice of carrier is not cosmetic here. PSA Airlines arrives on time 83.1% of the time; Frontier Airlines manages 67.8%. Sample sizes sit next to every figure, because a two-point gap across 1,589 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 36,433 | 81.7% | 74 min | 0.78% | B+ |
| Republic Airways | 9,181 | 80.7% | 80 min | 2.74% | B |
| Delta Air Lines | 3,014 | 80.3% | 95 min | 2.69% | B |
| SkyWest Airlines | 2,436 | 78.4% | 138 min | 2.01% | B |
| Frontier Airlines | 1,589 | 67.8% | 104 min | 2.45% | C |
| Alaska Airlines | 1,434 | 70.3% | 57 min | 0.84% | C+ |
| American Airlines | 1,267 | 77.5% | 93 min | 2.68% | B |
| Southwest Airlines | 1,202 | 73.3% | 51 min | 1.16% | C |
| PSA Airlines | 1,121 | 83.1% | 101 min | 3.66% | B− |
| Allegiant Air | 562 | 75.3% | 125 min | 0.36% | B+ |
PSA Airlines cancels 3.7% of what it schedules here, the highest in the table. A cancelled flight never appears in an on-time rate, so read that column alongside the punctuality one rather than after it.
Route by route
Busiest routes out of IAD
Route-level records vary far more than the airport average. These are the 25 busiest departures from IAD, each with its own on-time rate against the airport-wide 80.3%.
| Route | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| IAD to ATL · Atlanta | 3,946 | 78.4% | 89 min | 2.18% | B |
| IAD to DEN · Denver | 3,624 | 81.1% | 66 min | 0.69% | B+ |
| IAD to SFO · San Francisco | 2,828 | 78.8% | 81 min | 0.85% | B+ |
| IAD to LAX · Los Angeles | 2,427 | 80.3% | 65 min | 0.82% | B+ |
| IAD to MCO · Orlando | 2,204 | 80.9% | 77 min | 0.82% | B+ |
| IAD to ORD · Chicago | 2,024 | 74.7% | 70 min | 0.79% | C+ |
| IAD to CLT · Charlotte | 2,024 | 83.5% | 90 min | 2.96% | B |
| IAD to SEA · Seattle | 1,926 | 75.8% | 62 min | 0.99% | B+ |
| IAD to DFW · Dallas-Fort Worth | 1,920 | 77.3% | 97 min | 2.14% | B |
| IAD to IAH · Houston | 1,865 | 82.8% | 66 min | 0.64% | B+ |
| IAD to BOS · Boston | 1,487 | 75.4% | 76 min | 1.68% | B |
| IAD to EWR · Newark | 1,473 | 73.2% | 95 min | 2.24% | C |
| IAD to TPA · Tampa | 1,412 | 79.3% | 73 min | 1.06% | B |
| IAD to SAN · San Diego | 1,400 | 83.5% | 60 min | 0.43% | B+ |
| IAD to RDU · Raleigh | 1,334 | 83.5% | 73 min | 1.35% | B |
| IAD to PIT · Pittsburgh | 1,282 | 83.6% | 77 min | 1.64% | B |
| IAD to PHX · Phoenix | 1,154 | 79.5% | 66 min | 0.78% | B+ |
| IAD to CMH · Columbus | 1,129 | 80.4% | 76 min | 1.42% | B |
| IAD to LAS · Las Vegas | 1,129 | 84.3% | 66 min | 0.44% | B+ |
| IAD to DTW · Detroit | 1,091 | 75.6% | 109 min | 1.37% | B |
| IAD to AUS · Austin | 1,074 | 82.6% | 69 min | 0.84% | B+ |
| IAD to BDL · Hartford | 1,071 | 85.8% | 58 min | 1.68% | A |
| IAD to BNA · Nashville | 1,039 | 82.7% | 72 min | 0.67% | B+ |
| IAD to IND · Indianapolis | 1,022 | 82.8% | 85 min | 1.08% | B |
| IAD to CLE · Cleveland | 984 | 83.7% | 76 min | 1.12% | B |
Departure window
The best time of day to leave IAD
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 18 points, against 15 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am5,351 flights86.0%
- 8am–11am14,328 flights88.7%
- 11am–2pm10,874 flights84.1%
- 2pm–5pm4,030 flights76.2%
- 5pm–8pm15,908 flights70.8%
- 8pm–5am7,748 flights77.5%
Scale runs 60% to 95%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 88.7% of the time, against 70.8% for the evening window. That is 18 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on.
Across the year
When IAD runs late
IAD'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.
July is the worst month at 69.5% on time, 18 points below April, the best at 87.2%. 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.
Across the week, Tuesday is the strongest day at 83.8% on time and Sunday the weakest at 77.4%. 6 points is a smaller lever than departure hour, but it is free.
Delay causes
Why IAD 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 903,000 reported delay minutes.
- 34%Late-arriving aircraft
- 32%Carrier
- 25%National Airspace System
- 9%Extreme weather
- 0%Security
34% 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 903,000 reported delay minutes here, that single category outweighs weather by 4 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 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 88.7% on time here.
Cancellations sit at 1.39% against a national 1.80%, which is ordinary. Diversions add another 0.26%.
7.5% of arrivals land an hour or more late, close to the national 8.2%. 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 are the a little over an hour kind, which a normal layover absorbs.
58,239 flights sit behind these numbers, which is a large enough sample that the headline rate is not moving on noise. Where a sub-group falls below 30 flights the site shows a dash instead of a percentage.
What to do with this
Flying out of IAD
Put together: the calendar is the biggest lever here, not the carrier or the hour. April runs 87.2% on time and July 69.5%, a swing of 18 points. If the dates move at all, move them out of July before you think about anything else.
Common questions
IAD delay questions
How often is Washington (IAD) delayed?
About one flight in five arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 19.7% of the 58,239 flights in this analysis, against 22.6% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on Washington (IAD)?
PSA Airlines leads at 83.1% on time across 1,121 flights. Frontier Airlines is at the other end on 67.8%, a gap of 15 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on Washington (IAD)?
The 8am–11am departure window is the strongest at 88.7% on time. The 5pm–8pm window is the weakest at 70.8%, 18 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 Washington (IAD)?
July is the weakest month at 69.5% on time, compared with 87.2% in April. 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
Source: US DOT Bureau of Transportation Statistics, on-time performance data, June 2025 to May 2026. Updated monthly. How this data is collected.