Washington, DC · departure reliability

IAD

Washington Dulles International

Departures: 57,762
Period: September 2025 to August 2026
Carriers: 10
US rank: #34 by volume

Terminal building and aircraft stands at a US airport

Washington

Washington Dulles International 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 a little over an hour on average. That rests on 57,762 flights, of which PSA Airlines flew 967 at 83.8% on time.

PSA Airlines is the most reliable of the ten carriers covered here at 83.8% on time across 967 flights.

On time

81.0%

Departures arriving under 15 minutes late at their destination

Avg delay

80 min

Across delayed flights only

Cancelled

1.44%

National rate is 1.89%

Best carrier

PSA

83.8% on time here

These figures cover 58,000 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.

Carrier by carrier

Which airlines run best out of IAD

The choice of carrier is not cosmetic here. PSA Airlines arrives on time 83.8% of the time; Frontier Airlines manages 68.3%. Sample sizes sit next to every figure, because a two-point gap across 1,682 flights means less than a ten-point one.

On-time performance by carrier departing IAD
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines	36,915	82.1%	73 min	0.85%	B+
Republic Airways	8,421	81.5%	75 min	3.02%	B−
Delta Air Lines	3,159	80.4%	93 min	2.44%	B
SkyWest Airlines	2,514	79.5%	148 min	2.11%	B
Frontier Airlines	1,682	68.3%	95 min	2.79%	C
American Airlines	1,505	77.5%	103 min	2.06%	B
Alaska Airlines	1,196	74.8%	51 min	1.09%	C
PSA Airlines	967	83.8%	114 min	3.21%	B−
Southwest Airlines	872	76.1%	47 min	0.92%	B+
Allegiant Air	531	72.2%	106 min	0.94%	C+

PSA Airlines cancels 3.2% 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 81.0%.

Busiest routes from IAD by flight volume
Route	Flights	On time	Avg delay	Cancelled	Grade
IAD to ATL · Atlanta	4,003	78.0%	86 min	2.32%	B
IAD to DEN · Denver	3,387	83.1%	63 min	0.59%	B+
IAD to SFO · San Francisco	2,688	77.5%	72 min	0.71%	B+
IAD to LAX · Los Angeles	2,460	84.1%	60 min	0.73%	B+
IAD to MCO · Orlando	2,180	80.7%	76 min	1.10%	B
IAD to ORD · Chicago	2,106	74.7%	79 min	0.90%	C+
IAD to CLT · Charlotte	1,990	83.1%	96 min	2.66%	B
IAD to DFW · Dallas-Fort Worth	1,961	76.7%	106 min	1.63%	B
IAD to IAH · Houston	1,862	84.7%	71 min	0.48%	B+
IAD to SEA · Seattle	1,821	77.7%	64 min	0.99%	B+
IAD to EWR · Newark	1,560	77.1%	98 min	2.76%	B
IAD to BOS · Boston	1,524	76.9%	70 min	2.76%	B
IAD to SAN · San Diego	1,402	82.9%	58 min	0.71%	B+
IAD to TPA · Tampa	1,287	83.8%	70 min	0.78%	B+
IAD to RDU · Raleigh	1,275	83.1%	70 min	1.33%	B
IAD to PIT · Pittsburgh	1,213	84.3%	76 min	1.73%	B
IAD to DTW · Detroit	1,178	78.4%	107 min	1.27%	B
IAD to BDL · Hartford	1,082	85.9%	64 min	1.66%	A
IAD to CLE · Cleveland	1,076	84.1%	78 min	1.12%	B
IAD to LAS · Las Vegas	1,069	85.3%	71 min	0.56%	A+
IAD to MSP · Minneapolis	1,026	85.9%	97 min	1.46%	A
IAD to AUS · Austin	1,018	83.8%	72 min	0.79%	B+
IAD to BNA · Nashville	998	81.0%	79 min	0.80%	B+
IAD to IND · Indianapolis	984	83.8%	88 min	1.12%	B
IAD to PHX · Phoenix	979	81.2%	57 min	0.82%	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 16 points, against 16 points between the best and worst carrier.

5am–8am5,271 flights85.8%
8am–11am14,202 flights88.8%
11am–2pm11,364 flights83.4%
2pm–5pm3,536 flights78.3%
5pm–8pm15,738 flights72.4%
8pm–5am7,651 flights78.3%

Scale runs 65% to 95%.

Book the morning departure. Flights leaving between 8am–11am arrive on time 88.8% of the time, against 72.4% for the evening window. That is 16 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 15,738 flights scheduled in it.

Explore

Filter IAD departures 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 departures from Washington (IAD), the best departure window is 8am–11am at 88.8% on time and the worst is 5pm–8pm at 72.4%, a wide gap of 16.4 points. All US flights leaving 8am–11am ran 83.9%.

5–8am85.8%
8–11am88.8%
11am–2pm83.4%
2–5pm78.3%
5–8pm72.4%
8pm–5am78.3%

best all US flightsScale 60% to 95%.

Across the year

When IAD runs late

IAD's year swings by 14 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.

Darker means more delays. Figures are on-time percentages.April best, July worst

July is the worst month at 73.7% on time, 14 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. May was the busiest month here, with 5,474 flights.

Across the week, Tuesday is the strongest day at 83.9% on time and Sunday the weakest at 77.7%, a spread of 6 points.

IAD month by month

From Europe

Transatlantic routes into IAD

20 European airports send scheduled passenger flights to IAD, 24,413 flights a year in both directions by the DOT's international count. The DOT keeps no delay record for international flights; the UK routes carry the CAA's departure punctuality, and every route sets its departure airport's EUROCONTROL figures beside IAD's own record above.

Every Europe-to-US route

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 865,000 reported delay minutes.

Late-arriving aircraft
33%
Carrier
31%
National Airspace System
29%
Extreme weather
8%
Security
0%

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 88.8% on time here. The split is drawn from 865,257 reported delay minutes.

No single cause dominates. late-arriving aircraft at 33%, carrier at 31% and national airspace system at 29% split the 865,000 reported delay minutes between them. An even spread like this usually means the operation is running close to its designed capacity with no one obvious weak point, and it is the hardest pattern for a traveller to route around.

Cancellations sit at 1.44% against a national 1.89%, which is ordinary. Diversions add another 0.28%.

7.1% 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 a little over an hour, which a normal layover absorbs.

57,762 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 73.7%, a swing of 14 points. If the dates move at all, move them out of July before you think about anything else. 56,767 completed flights over 12 months sit behind that.

Common questions

IAD delay questions

How often is Washington (IAD) 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 19.0% of the 57,762 flights in this analysis, against 22.7% 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 83.8% on time across 967 flights. Frontier Airlines is at the other end on 68.3%, a gap of 16 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 88.8% on time. The 5pm–8pm window is the weakest at 72.4%, 16 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 73.7% on time, compared with 87.2% in April. Across the year that is 14 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.

Where to go next

Embed IAD’s on-time badge on your site

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<iframe src="https://delayatlas.com/embed/airport/iad" width="320" height="132" style="border:0;max-width:100%" loading="lazy" title="IAD airport on-time record"></iframe>
<p style="font:12px/1.4 sans-serif;margin:4px 0 0">IAD airport delay statistics from <a href="https://delayatlas.com/airports/iad">DelayAtlas</a></p>

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.