Washington, DC · departure reliability

IAD

Washington Dulles International

Departures: 58,021
Period: July 2025 to June 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 77.6%. 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 58,021 flights, of which PSA Airlines flew 1,032 at 84.1% on time.

PSA Airlines is the most reliable of the ten carriers covered here at 84.1% on time across 1,032 flights.

On time

81.1%

Departures arriving under 15 minutes late at their destination

Avg delay

79 min

Across delayed flights only

Cancelled

1.37%

National rate is 1.81%

Best carrier

PSA

84.1% on time here

These figures cover 58,000 flights between July 2025 and June 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 84.1% of the time; Frontier Airlines manages 69.7%. Sample sizes sit next to every figure, because a two-point gap across 1,631 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	36,559	82.3%	73 min	0.80%	B+
Republic Airways	8,917	81.8%	79 min	2.69%	B
Delta Air Lines	3,063	80.9%	91 min	2.45%	B
SkyWest Airlines	2,440	79.0%	139 min	2.05%	B
Frontier Airlines	1,631	69.7%	99 min	2.45%	C
American Airlines	1,368	77.2%	97 min	2.70%	B
Alaska Airlines	1,344	71.7%	55 min	0.97%	C+
Southwest Airlines	1,100	73.9%	51 min	1.09%	C
PSA Airlines	1,032	84.1%	104 min	3.39%	B−
Allegiant Air	567	73.4%	120 min	0.35%	C+

PSA Airlines cancels 3.4% 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 81.1%.

Busiest routes from IAD by flight volume
Route	Flights	On time	Avg delay	Cancelled	Grade
IAD to ATL · Atlanta	3,976	79.2%	88 min	2.06%	B
IAD to DEN · Denver	3,560	81.7%	66 min	0.62%	B+
IAD to SFO · San Francisco	2,787	78.2%	74 min	0.90%	B+
IAD to LAX · Los Angeles	2,454	81.8%	63 min	0.94%	B+
IAD to MCO · Orlando	2,176	81.7%	71 min	0.87%	B+
IAD to ORD · Chicago	2,054	75.2%	73 min	0.83%	B+
IAD to CLT · Charlotte	1,994	83.7%	90 min	2.76%	B
IAD to DFW · Dallas-Fort Worth	1,928	77.1%	104 min	2.23%	B
IAD to SEA · Seattle	1,884	76.6%	63 min	1.01%	B
IAD to IAH · Houston	1,869	83.7%	68 min	0.48%	B+
IAD to EWR · Newark	1,501	75.3%	89 min	2.27%	B
IAD to BOS · Boston	1,462	77.3%	73 min	1.92%	B
IAD to SAN · San Diego	1,400	83.6%	58 min	0.43%	B+
IAD to TPA · Tampa	1,366	81.2%	69 min	0.88%	B+
IAD to RDU · Raleigh	1,293	84.3%	72 min	1.24%	B
IAD to PIT · Pittsburgh	1,268	84.5%	79 min	1.50%	B
IAD to LAS · Las Vegas	1,108	85.1%	69 min	0.45%	A+
IAD to PHX · Phoenix	1,097	79.9%	63 min	0.82%	B+
IAD to DTW · Detroit	1,096	76.7%	107 min	1.55%	B
IAD to BDL · Hartford	1,092	86.2%	59 min	1.83%	A
IAD to CMH · Columbus	1,061	82.1%	78 min	1.41%	B
IAD to AUS · Austin	1,049	83.9%	66 min	0.76%	B+
IAD to BNA · Nashville	1,012	82.9%	76 min	0.69%	B+
IAD to IND · Indianapolis	992	83.8%	85 min	1.01%	B
IAD to CLE · Cleveland	985	84.6%	76 min	1.02%	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 17 points, against 14 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am5,324 flights85.8%
8am–11am14,303 flights88.8%
11am–2pm11,043 flights84.1%
2pm–5pm3,706 flights78.7%
5pm–8pm15,836 flights72.1%
8pm–5am7,809 flights78.5%

Scale runs 65% to 95%. Rows with fewer than 30 flights show a dash.

Book the morning departure. Flights leaving between 8am–11am arrive on time 88.8% of the time, against 72.1% for the evening window. That is 17 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 15,836 flights scheduled in it.

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.

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

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. May was the busiest month here, with 5,474 flights.

Across the week, Tuesday is the strongest day at 84.0% on time and Sunday the weakest at 78.3%. 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 856,000 reported delay minutes.

Late-arriving aircraft
34%
Carrier
32%
National Airspace System
26%
Extreme weather
8%
Security
0%

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 856,000 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 split is drawn from 855,924 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 88.8% on time here.

Cancellations sit at 1.37% against a national 1.81%, which is ordinary. Diversions add another 0.27%.

7.0% 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 are the a little over an hour kind, which a normal layover absorbs.

58,021 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. 57,071 completed flights over 12 months sit behind that.

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 18.9% of the 58,021 flights in this analysis, against 22.4% 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 84.1% on time across 1,032 flights. Frontier Airlines is at the other end on 69.7%, a gap of 14 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 72.1%, 17 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.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.

Key figures